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How to seal a french drain

Laying French drains for landscaping purposes can help prevent water damage to basements, but it doesn’t take long before the drain clogs with dirt.

On average, homeowners spend $1,000 to $5,000 to repair water damage to their basements. This can be a lot of money to spend when you consider that most homeowners’ insurance policies do not cover water damage.

When you are building any kind of french drain it is important that you make sure the entire system has been properly sealed before you start using it.

The most effective way to seal a clogged french drain is to wash out any debris, use a snake of some sort to clear the drain, remove roots, install a landscape fabric and then seal the wall or basement around with liquid rubber.

Beneath your landscaping lies a French drain that is designed to carry water away from the foundation of your home.

Inexpensive and easy to install, this system works as long as it remains open.

I’ve researched why you might experience water escaping your French drain in a seemingly ineffective way.

To ensure that the drain works properly, read this blog post to learn how to prevent and solve common seepage problems with French drains.

The functioning of a French drain system

What is a French drain, anyway? A French drain is simply a drainage system that is meant to remove excess surface water from the surrounding area. It might be in the form of a ditch along the perimeter of your yard (may be installed when you had new landscaping done), or it could be a series of pipes running under your lawn or driveway.

These drains can be as small as a curbside gutter, or as large as the open space around the perimeter of an entire sports field!

How does it work? A French drain pulls water away from wherever you need drainage and funnels it deep into the ground to a dry well, or some other type of sump pump.

They can be made from a variety of materials: PVC pipe and corrugated metal culverts are common, as well as porous stone such as crushed gravel (gravel that contains very little rock fines). It’s also possible to use fabric filter material like geotextile fabric, or even a DIY trench filled with gravel.

All of these materials allow water into the drain, but keep soil from washing away.

If you’d like to know more about French drains and whether they require an outlet, I have a blog post here that covers all that.

Why French drains leak

Lately, you’ve been noticing a slow leak in the gutter along the side of your house. You have a French drain, so you have no idea why it would be leaking all of a sudden.

In fact, if anything, the French drain has been keeping water away from your foundation for years!

I say “leaking” in the loosest sense of the word, by the way. If you are noticing puddles in your yard when it hasn’t rained in weeks, you probably have a failed French drain.

So what’s going on with your French drain?

Your French drain is a rudimentary drainage system and is clogged by sediment build-up or any other debris, so it can’t handle excess water.

According to New Castle County’s Clearwater Disconnection Pilot Program report, a French drain system should be cleaned and maintained or rerouted when it’s full of deposits of silt and leaves, or it can fail.

Well, French drains are meant to function with water flowing through them along the path of least resistance — just like how rainwater naturally flows downhill.

However, there are several ways that a French drain can leak.

You see, the French drain only has the capacity to hold so much water before it then overflows back onto your lawn or your walkway.

When this happens, you might notice a leak in the form of bubbling, efflorescence, mold, mildew, or seeping moisture near the pipe.

If water is filling up inside your French drain pipe and draining back out – then it’s probably time to clear the drain.

Sometimes, you might not notice any of this until it’s too late.

The excess water could be pooling around your foundation, for example, or sinking into your lawn.

How to seal a French drain

Having a French drain is great, but leaks can happen.

Beware of the signs that your French drain is leaking, and what you can do to fix it.

French drains are most often installed with gravel, which can serve its purpose well, but over time it will erode and clog the drain.

The best way to seal a French drain is to clear away any excess soil or vegetation that may be obstructing the pipe itself.

Here is what you can do:

  1. Dig out the uphill side of the French drain so that you can see the “lip” of the pipe.
  2. Uncover the drainpipe along the bank of your yard
  3. Using a hose or a plumbing snake to flush out any sediment, run water down the drain line with the hose extended all the way to the end. Turn on your outside spigot and run it for a few minutes
  4. Keep in mind that this might take a few hours, or however long it takes to run water all the way through your drain line
  5. This should clear away any dirt and sediment that may be clogging your drain.
  6. Clear out all vegetation or soil along the banks of your yard, as vegetation inhibits the flow of water
  7. Seal nearby wall or basement with liquid rubber
  8. Make sure that you have a dry well, or sump pump to catch the excess water from the French drain if it does overflow during heavy rain.
  9. Install fabric filter material or geotextile fabric in place of some of the gravel, and dig down an additional six inches to give it a better perch.
  10. Make certain that you have a cleanout at the lowest point in your drain pipe so that it is easy to access for future maintenance and cleaning.