The ultimate guide to french drains

Offering reliable landscaping services to homeowners in British Columbia since 2013

Picture of Natasha Maerz

Natasha Maerz

Owner/Office Manager

At back40landscaping, our goal is to educate homeowners on their potential landscaping projects, and we truly find that honesty is the best policy.

By doing so, we believe that people will be able to make an educated decision for themselves and their family.

 

This guide is a tool to educate homeowners on all things related to French Drains.

Keeping these things in mind when choosing a French Drain system will allow you to get a system that will do the best job for your yard, and set your expectations for the system.

What is a French Drain?

There are many types of drainage systems that can be installed on a property, including perimeter drains and downspout drains, and while the name French Drain sounds complicated, it really is just another type of drainage system that can be put in to alleviate a properties water issue.

Simply put, French Drains dry out the surface and subsurface of a lawn. They transport water away from one spot and into a designated area (discharge station), making them a great option for anyone looking to fix a wet, soggy yard.

By installing a French Drain, you can take your lawn from damp and spongy, and transform it into a dry space.

How are French Drains made?

Since there are many different layouts and materials that can be used to build a French Drain system, this example of how a French Drain is made is “best practice”. (Keep in mind that each contractor has a different way to instal a French Drain system.)

Steps Of Installing a “Best practice” French Drain System

  • BC1call is called to determine where underground utility lines are.
  • A private company marks all underground utilities. This is a very important step, as you do not want to deal with the headache and cost of someone hitting a utility line.
  • Any obstacles that will hinder machines from getting into your backyard are taken down, or moved, such as fence panels or bushes.
  • A discharge location is chosen. This is either by using a city storm drain/stormwater connection, ditch or other location.
  • The ground and all surrounding areas are protected with a plywood road, limiting the damage to your yard.
  • A sloped trench is dug with an excavator 16” deep and 16” wide. The trench is sloped so once the system is installed it can help the pipe do its job by bringing water to the discharge station.
  • The excavated soil is hauled away in a dump truck and disposed of.
  • Double punched filter fabric is placed in the trench, lining the bottom and the sides.
  • Baughman tile pipe is put on the bottom of the trench, and 1 ½” round rock is placed on top of the tile pipe.
  • The filter fabric is “burrito” wrapped around the entire system, and pinned together.
  • Top soil is placed on top of the trench.
  • The top soil is either seeded, or sod is laid on top.
  • The plywood roads are taken away, and the grass is raked.
  • The road and all areas that were used during installation are swept and cleaned.
french-drain-installation

Installation methods

It would be impossible to inform you of each type of install, so here are three typical installs we see.

Installation Method #1

Cost: $5,000-$9,000

Materials used: Big-o drainage pipe

Method: The French Drain trench is hand dug, big-o pipe is put in, and clay soil backfills the trench.

Pros of this method:

  • This option is the cheapest option because there are no disposal costs due to the original excavated soil being used to backfill the trench. No rock or fabric are used in this method, making the cost of materials go down.
  • It is DIY friendly, as it is relatively easy to install. No excavators, skids steers or dump trucks are needed.
  • Supplies are readily available at your local home renovation store.

Cons of this method:

  • This method has a short lifespan of several months-2 years before clay soils around the pipe compact and don’t allow water to get to the pipe. Also, while this compaction is happening, the pipe is becoming crushed, and/or filling with soil. Once the clay soil clogs the system, it is no longer serving its purpose as a drain.
  • Since there is no rock put in with this method, there are no void spaces surrounding the pipe. Without void space, the subsurface will not dry out.
  • Even though this method of install is the cheapest up front, in the long run it will be costlier when it needs to be dug up, disposed of, and redone. This means that your drain can double in price, costing you more than if you would have done a superior system up front.

Installation Method #2

Cost: $9,000-$13,000

Materials used: PVC drainage pipe, 3/4” clear gravel, single punched fabric

Method: The French Drain trench is dug with an excavator, ¾” clear gravel is dumped into the trench, pipe is placed on top of the gravel, more gravel is used to backfill, and fabric is laid on top.

Pros of this method:

  • PVC pipe will not crush like big-o
  • This pipe has large inlet holes close to the bottom, at the 5 and 7 o’clock mark.
  • There is some void space around the pipe as ¾” clear gravel is used to backfill the trench. This method is superior than backfilling with dirt.

Cons of this method:

  • This method is expensive compared to the big-o method due to the cost of installation and labor. PVC pipe is rigid, so if there are any curves around the existing landscape or trees that the pipe needs to curve around, it is time consuming to glue fittings on the pipe.
  • Due to the pipe only having two holes on the bottom of it, its needs to be set on top of gravel so that the holes do not get clogged. This means that water will always be in the gravel below the pipe.
  • The gravel under and around the PVC pipe will mix with the soil, as filter fabric is not used to encapsulate the entire French drain, just on top of the drain. This puts an expiry date on the system.

Installation Method #3

Cost: $13,000-$17,000

Materials used: Blue octane drainage pipe (Baughman tile), double punched fabric, 1 ½” round rock

Method: The French Drain trench is dug with an excavator, double punched fabric lines the bottom, and sides of the trench, and blue high octane drainage pipe (Baughman tile) is placed inside. 1 ½” round rock is used as backfill, and the fabric burrito wraps the whole system.

Pros of this method:

  • All of the materials and components involved in this method are rated for 200+ years.
  • The blue octane pipe (Baughman tile) has the largest inlets and numbers of holes in the pipe. The void spaces between the 1 ½” round rock dry up the subsurface quickly, allowing your yard to be used sooner.
  • Because the system is burrito wrapped, the soil cannot get into the trench, and will never clog. The tested filter fabric can pass 140 gallons per min of water, per square ft. allowing for optimal drainage, and the fabric will not slow down the water transfer.

Cons of this method:

  • This method has the highest cost due to the materials (High Octane pipe, fabric, and rock) involved in making it, the removal of soil, and the rock used in backfilling the entire trench.
  • Site access needs to be able to fit an excavator to dig the trench, and to allow for wheelbarrows and a skid steer to load dump trucks at the street.
  • This system is not DIY friendly due to the amount of soil being hauled out, taken away, and rock being brought into the site.

How much does a French Drain cost?

For a typical residential backyard, a French drain can cost anywhere between $5,000-$17,000.

*A typical residential backyard is anything that takes 30 min or less to mow.

How the layout affects the cost of a system

The layout of a French Drain is different for each yard, as many factors, such as how wet the yard is (how much water the system is going to have to get rid of), whether other drainage systems are present (downspout or perimeter drains) and the slope of a yard, change from property to property.

The layout of the pipe installed for a system is important because the pipe that is in the ground absorbs surface and subsurface groundwater, and makes it disappear to the designated area. The more water that gets into your system, the dryer your yard will be. This means that the more pipe that is placed in your yard, the better the drainage system.

Systems with more pipe have a higher cost due to the materials and labor of the French Drain installation.

How materials affect the cost of a French Drain system

There are over a hundred combinations of how a French drain can be installed.

This is due to the wide variety of different ways to combine all of the systems, materials and methods that can be used.

These systems, materials and methods all affect the cost of the French Drain system.

Materials that can be used in a French Drain system

Fabric (Two Options)

Single punched: This landscape fabric has half the number of punched openings as the double punched fabric, and can easily lead to clogging because it restricts the flow of water.

Double punched: This fabric has a high-water flow, and will not get plugged. It comes in different thicknesses for durability and lifespan.

Drainage Pipe (Three Options)

Black ADS brand French drain pipe (Big-o, with lime green stripe): This pipe is made up of recycled materials and has three small inlets sliced in every valley. It is flexible and quick to install, but clogs and crushes very easily. It is the cheapest French drain pipe, and the most used pipe locally.

White PVC perforated pipe: This pipe is a rigid pipe that is 3x the price of big-o. It has no flex to it, does not stretch, and can crack when the ground settles. Due to each pipe being 10’ long, it is the slowest to install, because each of the 10’ sections have to be primed and glued together. Lots of fittings are needed to get the pipe to curve around trees or other objects. Unless it is installed below the frost line (18 inches) it can crack when frozen.

Blue High-Octane pipe (Baughman Tile brand): This purposed built French drainage pipe was designed for the clay soil that the Fraser Valley has. It is extremely flexible, fast to install, and has an excellent crush rating. Due to its 8 massive inlets in every valley, there is open air exchange that can dry out subsoil much faster than any other option of pipe. Baughman tile is the most durable of all of the pipes, but is the most expensive option.

Back Fill (Three Options)

Existing soil: The trench drain can be backfilled using the existing soil that was excavated. This soil is usually clay, since yards with sandy soil do not typically need a drain put in. Using the native soil as backfill will work until the original soil compacts again. This gives you effective drainage for 2 months – 2 years.

¾” clear gravel: Backfilling the trench drain with gravel will allow some water to pass through, however, it only provides the trench with a little bit of void space. This lack of void space limits it’s storage potential in a heavy rain, or snow melt event, and never fully dries out the subsurface of the yard.

1 1/2” round rock:                                                                                                                         When round rock is used to backfill the trench, it allows for greater void space and air movement, creating an underground drying effect. When the subsurface is dry, it allows the soil to act as a sponge, and soaks up water during rainfall. Plant roots are healthier, and your lawn will not have a yellowish waterlogged look to it.

French Drain system trench

General Price Factors for a French Drain system

Some factors that can increase the cost of your French drain install

  • Putting down temporary plywood roads to protect surfaces from machinery
  • Tight spaces that do not allow excavators, loaders and other machinery (resulting in the use of wheelbarrows, shovels, and hand digging)
  • Obstacles that get in the way of the project (fences, trees, buildings)
  • Disposal of materials (soil, old pipe etc.) and the amount of time driving and hauling these materials.
  • Having to add a Sump system with electric pumps (depending on discharge station and the property).
  • Length of distance to discharge station
  • Tree roots (system may need extra pipe placed so that roots do not breach the pipe)
  • Marking the area for utilities (Private utility contractor should be utilized when BC 1 call lists utilities in the area)
  • What fabric, gravel and pipe are used in the system
  • Size and length of the system (see diagrams below)

Some Factors That Can Decrease The Price Of A French Drain Install

  • New construction with no new landscaped areas
  • Open site that allows machinery full access
  • Onsite place to dispose of soil

To truly decide what system and methods are best for you, and your yard, you need to decide whether or not you want to solve your water problems for good. Having to redo the system in a couple of months-years is not only frustrating, but costly, as your old system will need to removed and hauled away, before a new one can be put in.

How to budget for your French Drain instal

Why Does The Budget Come First?

It may seem odd that you would want to give your budget first, and then have a system designed for you, but there are a couple of reasons why your budget dictates what French Drain system you get.

 Your System Can Be Built Many Ways

The beauty of having a French Drain installed is that if your system is built properly and with the right materials, that section of your yard will be dry.

If you let the contractor know what system you would like (How much pipe you want in the ground etc.) the contractor will make you the biggest, best system that they can think of.

This might mean replacing your clay soil with sandy soil, adding in drainage pipe everywhere, and doing a full lawn renovation on your landscape, so that your grass is super healthy (healthy grass helps take surface water away from your yard).

You might be thinking that this option is great because you want your drainage problems solved, however, the largest, best system, is going to cost substantially more. (This is due to having tested filter fabric, not just landscaping fabric, perforated pipe called Baughman tile)

 This might be something that you are okay with, but before the contractor prices out your job, they need to know that you are willing to spend that type of money on a project.

If you are not, time will be wasted, and you can end up disappointed.

What If You Tell Your Contractor What Type of System You Want, And They Design It with That in Mind?

Speaking frankly, if you are able to tell your contractor what system you want, why are you not doing the job yourself?

When starting projects like these, we tend to let the contractor know what our ideas are, and what people have told us we should do, but really, why not let the experts tell us what we need?

By telling your contractor what your budget is, and what PROBLEM you are looking to have fixed, (in this case a drainage problem) they will be able to give you a solution that works to solve your problem (installing a French Drain), and stay within your budget.

Can The Contractor Actually Stay Within My Budget?

This is where your expectations of your French Drain system, and the price you can afford to spend come hand in hand.

If you are serious about your budget, your contractor will need to have an open and honest conversation with you about whether or not they can give you the system you want, for the price you can afford.

Sometimes, this is not possible, and you may have to either look at your budget and see if you have any wiggle room, or lower your expectations.

In rare cases you may need to put the project on hold until you can save up to get the system you truly want.

What To Think About When Choosing a Budget?

When choosing a budget for your French Drain system you have many things to consider.

  • What can I afford? (No project should put you in debt, or make you feel uncomfortable with the amount of money you are spending)
  • What are my realistic expectations for my project?
  • Will I be okay if my budget and my system do not provide me with everything I am wanting?
  • If my budget is not realistic, does my situation allow for me to put this project off? (In some cases, the project must happen, such as when a basement is flooding).

By providing a budget before having a French Drain system installed, you will be able to have a system designed for your own individual needs, and will ensure that you will get what you are looking for, at a price you are comfortable spending.

Remember, if you are not comfortable giving a budget to a contractor, you may need to reconsider working with them!

French- Drain- trench- pipe

What is the Lifespan Of A French Drain System?

The type of drainage pipe used in your French Drain installation is a big component on how long your system is going to last for.

The drainage pipes job is to carry any water that gets into the system and to a discharge station, and is the lifeline of your French Drain.

There are three different drainage pipes that are used when installing a French Drain: Big-O, PVC, and Baughman tile.

Each of these options of drainage pipe will work for your French Drain instal, but have vastly different lifespans.

Big-O Drainage Pipe

What Is Big-O Drainage Pipe?

Big-O drainage pipe is made up of recycled materials, and has three small inlets sliced in every valley.

This pipe crushes very easily compared to perforated PVC and Baughman tile.

French Drains Installed with Big-O Pipe

Most French Drains that are installed with Big-O do not have any filter fabric, and when there is no filter fabric wrapped around the drainage pipe, soil gets into the pipe and compacts.

The compacted clay soil around and inside the French Drain pipe prevents water from getting into the system.

Because Big-O crushes easily, it will not take long for the compacted soil to crush the pipe. Once this happens, the French Drain is unable to do its job.

How Long Do French Drains Made With Big-O Last?

French drains made with Big-O pipe last on average 2-24 months.

Perforated PVC Drainage Pipe

What Is PVC Perforated Drainage Pipe?

White perforated PVC pipe is a rigid pipe that does not have any flex to it, does not stretch and only has holes on the bottom of the pipe

French Drains Installed With Perforated PVC Pipe

PVC pipe is prone to cracking due to frost heave, ground movement, and even traffic from above from lawn mowers or cars.

Because PVC pipe only has holes on the bottom of it, it needs to be installed on top of 2-4” of gravel. Therefore, there will always be standing water in the trench just below the pipe.

The problem with standing water is that it causes roots to infiltrate the system, and those roots end up clogging the pipe.

Smooth walled PVC pipe also allows debris to build up inside of the pipe, and the gentle smooth flowing water does not have the power to disrupt the debris.

This debris can settle in the bottom or along the inside of corners of the pipe.

This compacted soil around the French Drain pipe stops the water from being able to get into the system.

How Long Do French Drains Made With Perforated PVC Last?

French drains made with perforated PVC pipe usually last 1-20 years.

Baughman Tile Drainage pipe

What Is Baughman Tile Drainage Pipe?

Blue High-Octane Baughman tile drainage pipe is purposed built French drainage pipe, and was designed for the clay soil that the Fraser Valley has.

It is extremely flexible, fast to install, moves with the ground, and has an excellent crush rating.

French Drains Installed with Baughman Tile Drainage Pipe

Due to its 8 massive inlets in every valley, Baughman tile drainage pipe is placed on the bottom of the trench, and there is open air exchange that can dry out the subsoil much faster than any other option of pipe.

This open-air exchange actually prevents roots from getting into the system since there is no water in the trench.

This type of system is built with filter fabric that gets burrito wrapped around the pipe and round rock, keeping the drainage pipe free of debris.

Because the pipe is corrugated, the water passes through it, creating ripples that actually clean the pipe and pull any sediment with it.

How Long Do French Drains Made With Baughman Tile Drainage Pipe Last?

French drains that are built using Baughman tile drainage pipe last forever (50-200+ yrs.)

As you can see, different systems last longer than others, and the longevity of each differs quite substantially!

Factors that affect the longevity of a French Drain system 

Filter fabric

 Filter fabric plays a big role in how long a French Drain system will last, because it is used to keep soil from getting into your trench and mixing with the round rock inside.

This is important, because keeping the round rock clean is essential to keeping the void space in your trench open.

Your trench needs void space to allow air to move openly around the trench, therefore creating an underground drying effect.

 If your system does not have any fabric, the French drain will run into an issue of its pipe being clogged with dirt and debris.

This dirt clogs up the pipe, and water will have a harder time getting to its discharge area.

Putting in a tested filter fabric will protect your pipe from getting clogged, and move the water in your trench faster.

Backfill

When backfilling a trench, the two materials that are typically used are soil and round rock.

What you use to backfill your trench will determine how fast water will be able to get into your French Drain system, and to its discharge area.

Using Soil to Backfill a French Drain Trench

If you are having water issues, it is fair to say that the soil you have in your yard is clay.

Clay soil does not allow water to go through it, and if used to backfill your trench, will prevent water from ever getting into your system.

If water is unable to get into your drainage pipe, it will continue to cause your yard to have pooling water and mud.

Using Round Rock to Backfill A French Drain Trench

When backfilling with 1 ½” round rock, your system will have an ample amount of void space due to the size of the rock that is placed in the trench.

Void space in a trench is important, because the greater amount of void space that is in the trench, the quicker your yard will dry.

Void space allows both the surface and subsurface of your yard to dry out quickly by allowing air movement in the trench, creating an underground drying effect. The water that is on top of your yard is able to go through the round rock, and into the pipe.

Once that water gets into the pipe, the pipe can take it to its discharge station, and your yard will be dry.

closed-french-drain

Do French Drains need to be maintained?

The maintenance required for a French Drain varies from system to system. How the French Drain system is made and what materials were used in the build, will determine how much maintenance needs to be done on the system.

Annual Maintenance of a French Drain System

Healthy Lawn maintenance for good drainage

Healthy grass is a step that is often overlooked when it comes to installing a French Drain. Healthy grass roots, plants and vegetation are what help the water pass through the clay soil in your yard and into your system. Without an abundance of roots penetrating deep into the clay soil water will sit on top of the lawn regardless of any system that is put in. The roots from the lawn, and plants play a vital role in allowing this water to follow the roots deep underground and into your French Drain.

Annual lawn maintenance will allow a French Drain to continue to work optimally. This maintenance for a healthy lawn includes Fertilizing, moss and weed control, aerating, and seeding.

Keep in mind that there are things that need to be done each week that will ensure that the lawn is in tip top shape, like mowing, raking leaves, and watering.

Annual maintenance for Open French Drains

An open French Drain is a French Drain with no fabric or sod on top, just a layer of round river rock. The reason a homeowner would choose to install an open French drain is that it can drain water faster than it can accumulate. The downside to this type of drain is that because it is open, any leaves or dirt and debris will clog up the round rock. Even if an open French Drain system is installed in an area that has little to no trees and bushes (which should be the only time one is recommended), the system should be periodically checked throughout the year to see if it is still working.

Annual maintenance for Surface Mounted Drainage Grate

In some cases, homeowners may want to Install a grate over top of the fabric in the French Drain instead of grass. While this will allow water to get into your system quick, the drain can get clogged very easily. Every month or so (depending on weather and how much vegetation is around the area) the grate should be checked to ensure that there is nothing blocking it.

French Drain Sump Basin Pump Annual Service

If a system has a sump basin pump, it is important to stay on top of its maintenance so that it is working and ready for when you need it. The last thing anyone wants to be doing during a big storm is trying to fix it. Sump pumps often spend long periods of time idle (ex. Summer when there is no rain fall) and operate intermittently when the water rises and fills up the concrete basin. This wear and tear on the system is why pumps burn out, which is why annual maintenance a sump pump will ensure that it is working at all times. This annual sump pump maintenance includes examining the pump for any rust or corrosion, cleaning the inlet screen and sump basin, and making sure the discharge pipe is free of dirt.

Drainage Pipe Clean-Out in French Drain Systems Without Filter Fabric (Big-O Drainage Pipe)

The reason French Drain systems should be installed with filter fabric is because filter fabric protects drainage pipe from getting dirt and debris into the system. If the system was installed without filter fabric, dirt will accumulate and compact in the drainage pipe. This dirt is a problem, because it stops the water from flowing freely in the pipe. To clean out Big-O drainage pipe, a company will need to be called in. This will need to get done yearly, because dirt and debris will always be able to enter the drainage pipe and accumulate.

5-Year Maintenance of A French Drain System

Sediment In the Pipe of Your French Drain System (Perforated PVC Drainage Pipe Only)

Perforated PVC drainage pipe is smooth walled, but this doesn’t mean that debris won’t fill up inside of it. Smooth walled PVC pipe actually allows debris to build up inside of it because the gentle smooth flowing water in the pipe does not have the power to disrupt the debris, and it can settle in the bottom or along the inside of corners. This means that the pipe will need to be cleaned out at least every 5 years by having a company come in and clear it out.

Drainage Pipe Root Cutting (Perforated PVC Pipe Only)

Another drawback to using perforated PVC pipe is that there will always be standing water in the French Drain system. Because it only has holes on the bottom, it needs to be installed on top of 2-4” of gravel, and there will always be standing water in the gravel just below the pipe. This water will attract tree roots that will find their way into the pipe. As the roots begin to clog up the pipe, they will need to be cleaned out by a jetting machine. This jetting machine can remove the roots from inside the pipe, but will not be able to completely rid the pipe of them. Days/months later the roots will have regrown inside of the pipe again. Therefore, this cleaning and regrowing will continue indefinitely.

French Drain Sump Basin Pump Major Service

Since sump pumps go through a lot of wear and tear, they should be serviced every 5 years so that they are doing its job to the fullest, and protecting the home in the case of a large weather event.  After ensuring the sump pump is in working order (checking the float, testing the valves) and that it does not need to be replaced, the basin that the sump is in needs to be inspected/ cleaned. Debris in the basin is a major cause of pump issues, as it can block the pump and prevent it from taking in any water

10-Year Maintenance of A French Drain System

Sediment In the Sump Basin of a French Drain System

If the system has lasted this long, there is a good chance that the sump basin is filled with debris. Sump pumps can become clogged overtime due to buildup of particles and other debris in the basin.

To clean a sump basin, the pump must first be removed. Next, the entry and exit of the sump basin will need to be checked for anything that could be clogging it, and any sediment at the bottom should be shovelled out, or vacuumed out.

New French Drain Sump Basin Pump

Even the highest quality sump basin pumps need to be replaced eventually. If budget allows, it could be helpful to buy two quality pumps so that there is always one on standby. You truly never know when a pump will fail and need to be replaced.

How much maintenance that is done on a French Drain system comes down to the fabric, pipe, and type of backfill that is used in installing the French Drain.  Consider having a system installed that will not only last you a long time, but that has limited maintenance that needs to be done on it.

clogged-big-O-drainage-pipe

What Determines How Dry Your Yard Will Be?

The Type of Soil You Have

If you have sandy soil in your yard, you most likely are not concerned about getting a French drain installed.

Sandy soil allows surface water to penetrate into the ground, and takes excess water away from your yard.

Therefore, you will not have pooling of water and will not need to fix any drainage issues.

If you have clay soil, the opposite is happening to your lawn. Water cannot penetrate through clay soil, so it sits as surface water on top of your lawn instead.

This causes a soggy, muddy, backyard and landscape. Between children and pets with muddy wet feet running in and out of your house, and canceled BBQ’s, water issues are extremely frustrating, and can cause some major stress.

The Health of Your Lawn

Another factor in how dry your yard will be is how healthy your grass is.

Healthy grass roots are what help the surface water pass through the clay soil in your yard and into your system.

Without roots penetrating deep into the clay soil, water will sit on top of the lawn regardless of any drainage system that is put in.

The roots from your lawn, and plants, play a vital role in allowing this water to follow the roots deep underground and into your French Drain.

The Amount of Pipe That Is Placed in Your Yard (The French Drain System)

The layout (and amount) of the drainage pipe placed in your yard is important because the pipe that is in the ground absorbs surface and subsurface groundwater, and makes it disappear to the designated area.

The more collected water that gets into your system, the dryer your yard will be. This means that the more drainage pipe that is placed in your yard, the better the drainage system.

The best layout is different for each yard and landscape.

How Does Budget Affect How Dry a Yard Will Be?

Clay soil is one of the major causes to a yard needing a French Drain. To get a yard that is completely dry, clay soil needs to be removed, and replaced with sandy soil.

This option is definitely an investment. Excavating 4” of soil from your entire yard can take a long time, depending on how large your yard is, and hauling soil off site gets pricy, especially when you take into consideration that soil expands 1.3x its size when excavated!

Replacing the excavated soil with sandy soil takes time, and again, hauling costs.

If removing your clay soil is not an endeavour you want to take on, you can focus on the amount of pipe that is placed in your yard.

Simply put, the more drainage pipe you have in your yard, the faster the water will get to its discharge station.

The more pipe you have, the more labor and material costs there will be. To give an example, 100 ft of pipe will cost around $5,000, while 1000 ft of pipe will cost roughly $41,000.

That is a huge cost difference, and is going to be based on how big your yard is, and how serious you are about fixing your drainage problems.

Healthy grass is something that takes time, effort, and ample watering, but is something that should not be overlooked if you are truly wanting to fix your water issues.

Even a yard with the biggest/best system will benefit from healthy grass. The cost of keeping your grass healthy will depend on what type of grass you have in the first place (is it fairly healthy, patchy, or non-existent), and how you are going to maintain it.

If your grass is already established, the cost of getting your lawn healthy is nothing compared to the benefits you will see when you are able to fully enjoy and use your yard.

Factors That Impact the Speed Of A French Drain System

A French Drains performance can be broken down into 3 sections and as we are about to discover they all have to function to get results.

Often times a system that is not working has a component that has failed, or was not designed correctly.

How Much Yard Water Needs to Be Drained?

The first question we must ask when designing a system is how much water will the French drain be responsible to drain?

French drains are installed in the yard or lawn, and may also be responsible to drain rain water that has run onto the lawn from a patio, sidewalk, and sometimes even a driveway.

In most cases a French Drain is not responsible for collecting rain water that falls onto the roof, and is collected in the gutters and downspouts.

That drainage system is called a downspout drain. However, it is not uncommon for downspouts to be directed onto the surface of the lawn.

While a French drain can eventually drain this, it will create more standing water that will take longer to dry after a rain event.

When setting your expectations for how fast your French drain dries up an area, consider how much water is involved.

Limiting the amount of water directed onto your lawn will decrease the waiting time after a rain event.

How Does the Water Get from The Surface of The Yard into The Drainage Pipe?

How surface water gets into your French Drain drainage pipe is called infiltration.

This is by far the most important and complex part of the system.

Almost every yard that has a drainage issue is caused because of clay soil. Clay soil does not percolate well, and is the reason you have standing water.

Yards with sandy soils drain into the earth as fast as it can rain.

Clay soil effects a French drain in two main ways.

1: The first is it creates standing water on the surface of a lawn. If you have ever made a clay bowl as a child you will remember that water will stay in this bowl almost indefinitely.

Light clay soils will eventually pass water, but heavy clays will almost never allow water through it on its own.

Lawns with healthy grass roots will help to penetrate this clay soil, and provide microscopic paths for the water to get through.

It generally takes a year for the grass to establish healthy roots, however if this is in a shady area, or an unmaintained area, the grass may never provide adequate roots to penetrate the clay soil.

2: The second reason clay soil is a problem for French Drains is once the water does eventually make it into the ground, it moves laterally very slowly.

This slow process causes water to back up on the surface, and if not addressed will prevent the system from ever draining the water.

Best practises to overcome clay soil:

  • Install a French drain system with void spaces underground (large round rock). The void spaces will dry out the clay between rain events, and instead of starting a rain event with saturated soil, you will go into a rain event with dry soil that is capable of absorbing much more water.
  • Replace the top 2-4” of soil in the yard with free draining sandy soil. This will allow the water to get below the grass and move laterally to the nearest French Drain trench.
  • Increase the size of a French Drain system. The closer together the Drain trenches are excavated the shorter the distance the water has to travel to be removed. This will increase the speed in which your lawn dries up.
  • Grade the area to slope to a low spot and instal the French drain system there. This way the water will run on top of the grass and move quickly to a centralized location to be collected from.

Another component of infiltrating a French Drain system is the fabric layer the water must travel through.

Most landscape filter fabrics do not pass water fast enough to use. This means the fabric will plug up, and greatly reduce the speed in which the area dries up.

There are specific fabrics that are tested to use in clay soils, and that pass water even under the most extreme cases.

In some cases, the highest rated filter fabric may still not be fast enough, and you may want to Install a grate over top of the fabric instead of grass.

In extreme cases you could have an open French Drain system where there is no fabric or sod on top, just a layer of round river rock. It would be important not to do this in a heavily treed or trafficked area where the system would get plugged up from debris.

Installing an open French drain around a patio however, would not only look great, it would drain the water faster than it can accumulate.

Where Does My French Drain Water Go?

Once the water is inside the fabric of a French drain system the water will flow virtually unrestricted to the lowest point in the system.

The best French drain systems use a pipe at the very bottom of the trench and surround it with large 1.5” round rock. There is so much void space underground that between the pipe and the round rock the system can move 400-800 gallons per minute.

The French drain system itself is almost never what effects the speed in which your yard dries out, as its so much faster than the intake portion of the system.

Most French drain systems discharge to a concrete sump where any sediment or debris can settle to the bottom of the basin.

From here its drained to a city storm water connection, ditch, lower area that can be flooded, etc.

As long as this capacity to intake the water isn’t exceeded, then the water will not back up the French drain trench.

When having a French Drain system installed, take the time to really think about what you want the outcome of your yard to be after the project is over. Consider all of the factors (lawn health, soil, and amount of pipe) and really think about how you use your yard, and if you value useable lawn space.

Not only will a dry lawn make your yard more enjoyable for everyone, but it will add value to your home.

drainage-sump-basin

Common French Drain Mistakes/Problems

Backfilling The Drainage Pipe with Dirt

When backfilling a French drain, it may seem like a good option to use the dirt that was dug up so that you do not need to worry about where to dispose of it.

The problem with using the excavated soil is that native clay does not allow water to go through it. 

When you backfill with dirt, no fabric is placed in the trench, and when there is no fabric in the bottom of the trench and encapsulating the drain pipe system, soil will end up in the pipe.

This means that even if water eventually makes its way through the clay soil and into the system, the likelihood of the drain pipe clogging is high, and the water will still have nowhere to go.

Contractors Or Clients Wanting to Save Money

With the cost of living and housing, it is no wonder homeowners do not want to spend their hard-earned money on a french drain installation instead of a vacation.

French drains that may have a higher price usually have a more durable pipe that does not crush, and fabric encapsulating the trench to keep the soil from mixing with the rock in the system.

Large rock is used to create void space in the trench, which dries out the system.

This system will last a century, while a lower cost version will last 2-24months.

 No Original Drainage System

Surprisingly enough, when new homes are built, yard drains are not included. These systems are looked at as “extra” by municipalities and builders.

In our wet climate with excessive ground water, it really should be mandatory to install a drainage system for some properties and avoid altogether the drainage issues that inevitably occur.

For people living on these properties without a drainage system that live at the base of a hill, or have their neighbour’s above them, their yard is only going to be useable for only about half of the year due to an inundation of surface water runoff in the yard.

 Without a system, their grass may be unable to grow, and the space can be unusable for pets, and children.

When people buy a house, they want a useable yard, and nobody wants to be dealing with drainage problems and excess water in their new place!  

This is something to be aware of when moving into a house, new or old.

Underestimating How Much Rain the Fraser Valley Gets

The Fraser Valley averages 174 rainy days per year. Heavy rains and stormwater are a real issue where we live and it results in a lot of excessive groundwater! 

If you do not have a French drain system put in in your yard, you will most likely need to wait a day if not more, to be able to use your backyard space.

This means having to wait to mow your grass, being unable to BBQ, and keeping children and pets inside.

It can be frustrating having to postpone your weekend plans because it rained the day before and your yard has yet to dry out.

This is especially annoying if you have a day off and are trying to do yard work. Luckily, if you put in a French drain system, not only will you be able to enjoy your yard much sooner than others, you will be able to use it for longer periods of time.

This is where having a French drain system really pays off.

Ignoring 25% Of Your Lawn Drainage Solution

Putting in a French drain system is a 75% solution for your backyard drainage. The first part of the solution is to have a French drain installed.

The second step to think about is growing healthy grass, with healthy roots. Healthy roots from grass, plants and vegetation are what help the water pass through the clay soil in your yard.

If you are noticing that a French drain you have already installed is not getting enough of your yard dry, try getting your grass to grow, or mow higher, and see if this makes a difference.

Using Untested Fabric, And Not Encapsulating the Entire System

One of the reasons that fabric is used in a French drain install is so that the soil does not get into the system and mix with the gravel.

One problem with using some kinds of landscape fabric is that the water pools on top of it. When this happens, the water never has a chance to get into the drain pipe, and be taken to its discharge station.

Before using any fabric in your French drain pipe system, it is important to know if the manufacturer specifications of the fabric are correct.

We tested filter fabric that stated that it could move up to 95 gallons of water per min, per square ft.

This fabric did not do what the specifications stated, and the flow of water pooled in our test pail.

Some people choose not to use fabric for this reason. Luckily, there is fabric out there that can keep up with the water flow, you just need to make sure to test it first.

The reason it is important for fabric to encapsulate the entire trench is that once installed, no soil can get into the gravel, and your trench will last centuries.

 If the fabric used does not line the bottom of the trench, as well as the sides, and top, the soil will mix with the gravel.

Once this happens, you are putting an expiration date on the system, and it will eventually clog.

Not Digging the French Drain System Deep, Or Wide Enough

When digging a trench for a French drain pipe system the deeper and wider that the trench is dug, the more surface area there will be within the trench.

This is important, as the surface area of the trench dries out the subsurface of the yard.

Other factors that help the subsurface stay dry are the rock that is used in the system. Big round rock allows a bigger void space in the trench.

This air movement creates an underground drying effect.

The big void space made by the rock also acts as an underground reservoir for the water entering the trench.

This is particularly helpful when there is heavy rainfall or large amounts of snow melting at once.

Not Having a Proper Discharge Location

City storm drains and ditches usually have enough capacity to act as a great discharge location for your French drain pipe system.

If the city storm drain or ditch are at the front of your house and your system is at the back, more pipe will need to be placed to get to it.

Since adding more pipe and labor will bring up the cost of the install, you may want to seek other alternatives, such as a rock pit.

Rock pits are a common method used as a discharge location, but unfortunately, they usually do not have enough space to hold the water that you are trying to get rid of.

By early winter your system could get full, and will stay that way for most of the year.

 Cost Of Doing A High-Performance System

A high-performance system may come with a higher price tag than a “typical” system.

When using pipe that does not crush, rock instead of gravel to give more void space in the trench, and fabric to protect the trench from getting soil into it, it will last you centuries.

Your family and pets will be able to enjoy your backyard any time they wish, and you will never have to worry about the system not working, or having to redo it.

Most importantly, having a high-performance system put in will increase the value of your house.

A complete French drain system typically costs more than people think, costing between $10,000-$17,000.

A complete system includes protecting the existing landscape, installing the system, and site remediation.

 Not Educating Yourself Before Hiring a French Drain Contractor

A French drain system install can seem simple enough, and may appear to be a relatively small undertaking.

There are 100’s of combinations and different materials and ways that French drains can be put in, and it can get quite overwhelming to see all of the options available.

It is a good idea to educate yourself before you hire a contractor, whether you know them or they were recommended by a friend or neighbour.

By doing your research and understanding what system they will be putting in, and why they like to do it that way, you can feel secure in your choice to hire them.

YouTube, Google reviews, and the contractor’s website are all great resources to help you educate yourself on their scope of work, and what the project entails.

It can even give you great insight on the contractor themselves!

The Placement of The Pipe

The purpose of the pipe in a French drain system is to “carry” the water away from the area that is water logged.

The placement of the drainage pipe really makes a difference in how the drain works, and for how long it will work for.

When the pipe is placed on top of the rock, there will always be standing water under the pipe.

If you have standing water, tree roots will seek out the water and infiltrate the system. As the roots begin to clog up the pipe, they will need to be cleaned out by a jetting machine.

This jetting machine can remove the roots from inside the pipe, but will not be able to completely rid the pipe of them.

Days/months later the roots will have regrown inside of the pipe again. Therefore, this cleaning and regrowing will continue indefinitely.

A better drainage pipe to use for a French Drain system would be perforated pipe.

Perforated pipe (Baughman tile) is placed directly onto the bottom of the trench that is layered with tested filter fabric, not on gravel or rock.

Because of this placement, there will be no standing water in the system, and the water can easily get taken to its discharge station.

 

Baughman- tile- and- round- rock- in-French-Drain

The best French Drain system you can get

Price Of This System

 $13,000-$17,000+ Depending on Linear Feet of drainage  pipe that is getting installed.

Layout

The layout for the best French Drain system you can get is going to differ from yard to yard. This layout will allow the water more opportunities to get into the pipe, and away from your yard.

Drain Materials

Blue High-Octane Baughman Tile

This Blue pipe was purpose built for the clay soil that the Fraser Valley sees, and was designed specifically for French Drain systems.

It is extremely flexible, fast to lay in the trench, and has an excellent crush rating.

Due to its 8 massive inlets in every valley, open air exchange can dry out the subsoil much faster than any other option of pipe. Baughman tile is the most durable pipe you can get.

Double punched tested filter fabric

The reason tested filter fabric is used in the best French Drain system is so that soil will not be able to get into the system and mix with the gravel.

Keeping the gravel clean is essential in keeping the void spaces open, which avoids clogging and allows the water to runoff quickly.

It also allows air to freely move around which creates an underground drying effect.

The double punched filter fabric in this system is tested, and has a high-water flow. This fabric allows water to get into the pipe, and taken to its discharge station. While MOST fabrics claim to have a high flow rate they usually do not, and this can lead to drainage problems.

Most contractors that have had a bad experience with fabric will tell you not to use any because it will plug up.

The facts are that using tested, DOUBLE punch filter fabric will not plug up, and will allow over 100 gal/Min/square ft to pass through it, even in heavy clay situations.

1 ½” Round rock as backfill

An ideal backfill for a French Drain system is 1 ½” round rock. When backfilling with 1 ½” round rock, your drainage system will have an ample amount of void space due to the size of the rock that is placed in the trench.

Void space in a trench is important, because the greater amount of void space that is in the trench, the quicker your yard will dry.

Top Soil

Top soil, or high-quality compost, is put on top of the trench.

This soil has no clay content, and water is able to pass through it and into the trench quickly.

A bonus to this is that Compost retains enough moisture in it to allow the grass in your yard to stay healthy, and healthy grass is a must for a French drain system.

Turfgrass

The roots from your lawn and plants play a vital role in allowing this water to follow the roots deep underground and into your French Drain.

The best French Drain system needs healthy turf.

Method of installing the best French drain system (Same method as best practice)
  • BC1call is called to determine where underground utility lines are.
  • A private company marks all underground utilities. This is a very important step as you do not want to deal with the headache and cost of someone hitting a utility line.
  • Any obstacles that will hinder machines from getting into your backyard are taken down, or moved, such as fence panels or bushes.
  • A discharge location is chosen. This is either by using a city storm drain/stormwater connection, ditch or other location.
  • The ground and all surrounding areas are protected with a plywood road, limiting the damage to your yard.
  • A sloped trench is dug with an excavator 16 inches deep and 16 inches wide. The trench is sloped so once the system is installed it can help the pipe do its job by bringing water to the discharge station.
  • The excavated soil is hauled away in a dump truck and disposed of.
  • Double punched filter fabric is placed in the trench, lining the bottom and the sides.
  • Baughman tile is put on the bottom of the trench, and 1 ½” round rock is placed on top of the tile.
  • The filter fabric is “burrito” wrapped around the entire system, and pinned together.
  • Top soil is placed on top of the trench.
  • The top soil is either seeded, or sod laid on top.
  • The plywood roads are taken away, and the grass is raked.
  • The road and all areas that were used during installation are swept and cleaned

Using these methods and materials, this system will last centuries, giving you a lawn you and your family can enjoy for generations to come.

This system is for people who really want to solve their water issues, and do not want to replace their system in the future.

French- Drain- design- layout- 3

Frequently asked questions about French Drains

What Area of My Yard Should My French Drain Be Installed In?

When having a French Drain installed, your trench should be placed in the lowest part of your yard.

This way any water from rain or your roof will be forced to go into your trench where it can then be carried away.

If your French Drain is placed at the highest part of your yard, water will not be able to make it into your drain because it will naturally gravitate to the lowest point in your yard.

Why Is Water Pooling in My Yard?

If your yard has heavy clay soil, water won’t be able to find its way into your trench, and will sit on top of your lawn, causing it be wet, unless you have healthy establishes grass.

If you replace your clay soil with sandy soil or grow healthy grass, the surface water will be able to easily percolate through the soil, and into your trench.

Once the water makes it to your trench, the system can take it to its dedicated discharge area.

What Can I Do Make My Lawn Dry Out Quicker?

 While French Drains dry out within 12-36 hours after a rainfall, if you want to dry out your yard even quicker, you may want to upgrade your system.

A drain grate can be added to your French Drain system to allow water to flow directly into the trench, and let the water be discharged faster than having to wait for it to go through the clay or sandy soil, and then into the system. 

Another option is to actually leave your trench open.

Leaving your trench open (not backfilling with soil) means that the water will be able to find your trench right away, and the exposed rock adds a nice décor element to your space.

The option of leaving your trench open is a good one for homeowners who have an open space in their yard, with little vegetation.

If your yard has a lot of trees around the area, an open trench may cause you problems, due to leaves and other dirt and debris getting into the system.

This debris can clog the rock, and not allow the rock to drain the water going into your trench.

Should You Use Filter Fabric with A French Drain System?

Filter fabric is used in a French Drain system to keep soil from getting into your trench and mixing with the round rock.

This is important, because keeping the round rock clean is essential to keeping the void space in your trench open, and to allow the water in your trench to move freely and to the discharge station quickly.

Your trench needs void space to allow air to move openly around the trench, therefore creating an underground drying effect. Proper fabric allows all of this to happen.

Not all fabric that is used for French Drains are equal, so if your system has fabric but is still not performing well, it could be that your fabric has not been tested for a high-water flow.

Is It Bad If My French Drain Does Not Have Fabric in It?

 If your system does not have any fabric, you are probably running into an issue of your pipe being clogged with dirt and debris.

This dirt clogs up your pipe, and water will have a harder time getting to its discharge area. Putting in a tested filter fabric will protect your pipe from getting clogged, and move the water in your trench faster.

How To Choose a Layout for My French Drain?

The layout of the pipe and how much pipe is placed in your French Drain system is important because the pipe that is in the ground absorbs surface and subsurface groundwater, and makes it disappear to the designated area.

The more water that gets into your system, the dryer your yard will be.

This means that the more pipe that is placed in your yard, the better the drainage system.

The best layout is different for each yard and space.

The layout of your French Drain system should be based on your budget, and how quick you want your yard to dry after a rainfall.

Keep in mind that you can always upgrade your system later down the road if you want your yard to dry out faster.

Just remember that if you are going to upgrade, the original system would have needed to be built “properly” to allow the system to function together.

In other words, if the old system was built with Big “O”, and the new system was built with Baughman drainage tile, one side of your yard is going to need to be replaced sooner than the other, and will always dry faster.

What Type of Discharge Station Should a French Drain Have?

A discharge station is where all of the water from your trench ends up, and a common reason that your French Drain is backing up could be that yours may not be established correctly.  

Your discharge station should be big enough to handle all of the water that is being taken to it, and needs to be placed at the lowest point of your yard.

It is up to nature where your discharge station is placed, so if it is not possible to put one in the lowest spot of your yard, water will not be able to reach it.

Because of this, a pump will need to be put in to allow the water to get from your trench to its discharge station.

Other options for a discharge station if your yard will allow include a ditch, sump pump, or even a low area in your yard that you do not use that you can flood without it affecting you.

Whatever you choose, it must be able to do its job of collecting the water, otherwise your French Drain will not be able to live up to its full potential.

Hopefully this guide has given you greater insight into what to expect with a French Drain instal, and has answered most of your questions regarding French Drain systems.

Thank you for taking the time to read this guide. We look forward to helping you with your French Drain installation!