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French Drain Not Working: the Causes

Last modified: 2022-07-25 | Approximate reading time 4 mins

Léa Plourde-Archer

The french drain plays a highly important role in preserving your home's integrity, as water accumulating near the foundations can seriously damage a home and lead to expensive renovations.

Unfortunately, french drains can break down. In order for the drain to be able to fulfill its role properly again, it's important to identify what is causing it to malfunction.

What causes issues with a french drain?

A few important details

A French drain (or foundation drain) plays several roles: it ensures that rainwater is drained from the ground to be directed to a storm sewer or a cesspool, in addition to being very useful if you have drainage problems with surface water on your property.

It also prevents water from accumulating at the foundation level, as it is installed underground all around the perimeter of the house. Therefore, having a functional French drain can save you the inconvenience of experiencing water infiltration inside your basement.

Before we talk about the reasons why your french drain might not be working, it should be known that it not functioning properly is not necessarily a sign that it is broken; it may also have reached the end of its lifespan. The operating life of a French drain is around thirty years and can vary depending on the type of soil in which it has been installed.

The types of soils

drain pipe on soil_renoquotes

Regarding french drains, each type of soil has its pros and cons: 

A soil composed of stones and/or gravel can break the drain if a large stone exerts continuous pressure on it. French drains are quite rigid (in order to guarantee their longevity), but if a rock is creating pressure over a long period of time on one of the drain walls, this could eventually end up causing damage.

On the other hand, soil that mainly consists of sand has fairly low water content, but can easily clog a French drain due to the small fine particles that may be likely to seep into it over time.

Soils rich in iron particles can create iron ocher in the soil, a thick, reddish sludge that may cause the drain to block. Indeed, because of its thickness, the mud will have difficulty entering the drain to be evacuated as is the case with water. Therefore, it will accumulate on the walls of the French drain and completely block the openings.

Clay soil also tends to cave in during periods of drought. These types of soil movements can affect the French drain, as its slope must always be roughly the same to function properly.

If you have trees on your property, it's possible that one of them may have taken root around or inside the French drain - in which case its ability to drain water will be greatly affected. To fix this issue, the roots will have to be removed from the drain.

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Improper installation

Installing a French drain must be done correctly from start to finish, that is, by respecting currently established standards and regulations. Otherwise, its operational life will be greatly affected. This is why we strongly recommend that you hire professionals to diagnose, install, maintain or repair the French drain on your property.

It is very important to install it properly, as a French drain that is not set up with a negative slope towards its drip point will inevitably end up being clogged. Replacing a French drain is quite expensive: it's better to ensure that the installation is well done in the first place.

In simple terms, a French drain is a pipe that sends water from the foundation to the sewer. Gravity is the only thing it relies on to do its job. If it isn't well installed, the water will not go where it needs to go, because the slope creating the flow won't be steep enough.

If a joint between two parts of the French drain is poorly made, the drain risks weakening at this level and the components of the soil will seep inside. A well-installed and maintained drain will at most require a partial repair if a portion of it is damaged for various reasons.

It should be noted that old French drains made of terracotta (particularly those installed in the 1960s) are especially vulnerable to this type of problem. These drains were installed in such a way that their different sections were only juxtaposed one after the other, without any joints. That's why this type of drain is more likely to be invaded by roots that will make their way inside to clog it over time.

Exterior layout

It's always pleasant to create a yard layout that suits your aesthetical preferences. Therefore, having to take into account the effective drainage of your landscaping may not be attractive at first glance, but land that is flooded by surface water is probably even less so.

If your landscaping plan involves creating slopes, be sure to lay them out so that water will flow away from the perimeter of the foundation. Try to opt for a slope that goes towards the front of the house, away from the foundations and above all, make sure not to discharge water runoff towards your neighbours' yards!

slope towards a sewer_renoquotes

Before you plan out your landscaping, it can be useful to survey the existing conditions of the land. In doing so, you know exactly where to go to maximize the natural drainage of your land, which will put even less pressure on the French drain.

In a nutshell

A properly installed and periodically maintained French drain can extend its operational life and slow down the need for repairs. If you combine preventive maintenance of your drain and good management of the capacities of your land, the drain will do its job very well, effectively protecting your foundations from water infiltration.

Image source: Freeimages 

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