French Drains FAQ

Offering reliable landscaping services to homeowners in British Columbia since 2013

Natasha Maerz

Natasha Maerz

Owner/Office Manager

Table of Contents

Here is a list of our most common questions related to French Drains, and their answers.

Not seeing the answer to your question? Send us a message and we can answer it for you, or go to our dedicated page about French Drains.

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.

French-Drain -trench- layout

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)

  1. BC1call is called to determine where underground utility lines are.
  2. 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.
  3. Any obstacles that will hinder machines from getting into your backyard are taken down, or moved, such as fence panels or bushes.
  4. A discharge location is chosen. This is either by using a city storm drain/stormwater connection, ditch or other location.
  5. The ground and all surrounding areas are protected with a plywood road, limiting the damage to your yard.
  6. 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.
  7. The excavated soil is hauled away in a dump truck and disposed of.
  8. Double punched filter fabric is placed in the trench, lining the bottom and the sides.
  9. Baughman tile pipe is put on the bottom of the trench, and 1 ½” round rock is placed on top of the tile pipe.
  10. The filter fabric is “burrito” wrapped around the entire system, and pinned together.
  11. Top soil is placed on top of the trench.
  12. The top soil is either seeded, or sod is laid on top.
  13. The plywood roads are taken away, and the grass is raked.
  14. The road and all areas that were used during installation are swept and cleaned.

What is the cost of a French Drain?

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

There are many different factors that can make the cost of a French Drain system go up and down. To get more information on what a French Drains costs, check out “How much do French Drains cost?”

How long do French Drains last?

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

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

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

What is the lifespan of a French Drain system? Will give you more insight on what to expect for how long your system is going to last.

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.

french-drain-installation
Baughman- tile- and- round- rock- in-French-Drain

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.

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At back40landscaping we build our French Drain systems with methods and materials that will last homeowners decades.  Let us take care of your French Drain needs today!