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Residential drains: the different types

By Isabelle Ladouceur-Séguin|6 min|November 2021

As a claims adjuster, you hear about all kinds of drains in your work. To help you distinguish them (and better understand what your policyholders are talking about!), here is an overview of each type.

Nowadays, most houses have drains to prevent water infiltration. In fact, only older houses may not. But with the variety of drainage systems used over the years (including the latest ones), it's easy to confuse them.

If you are a claims adjuster, you may have trouble understanding which drain your client is telling you about. In that case, you're in luck! We've put together a short guide to residential drains to help you out. Read on to learn about the different types of drains, their uses and how they work.

Foundation drains

In Quebec, all homes built after 1955 are equipped with a foundation drain. Their purpose is to protect the foundation from water seepage. To do this, they collect rainwater that accumulates in the soil around the house before channelling it into the sewer system.

The two main types of foundation drains are the French drain and the interior foundation drain.

French drains

A French drain is a system of pipes buried around the home's foundation and covered with gravel. This allows the rainwater to trickle down faster. A slight slope in the pipes allows the water to be directed to the sewers.

There are several types of French drain pipes:

  • Terracotta. Mostly found in older buildings, it consists of several sections of pipe-shaped clay tiles spaced slightly apart. Water seeps through the space between the tiles before being redirected away from the foundation.
  • Agricultural. This type of drain uses slotted pipes made of corrugated plastic, which makes it more flexible.
  • BNQ. This type of drain is made of PVC, a smooth, hard plastic. Its hole are much larger that those of agricultural drains.

Interior foundation drains

Interior foundation drain are very similar to French drains, except they run along the inside of the foundation walls instead of the outside. It collects the groundwater under the concrete slab and drains it out of the basement with a pump.

Linear drains

This is a V- or U-shaped channel covered with a grate. It has a slight slope that carries water to the sewer.

Linear drains are usually used to move rainwater from one place to another. They are useful for getting rid of large puddles or to keep a terrace dry. They can be found in a variety of materials:

  • plastic
  • ductile iron
  • galvanised steel
  • stainless steel
  • etc.

The choice of material depends in part on the weight the channel must be able to bear. For example, a parking lot linear drain must be stronger than a terrace one.

Infiltration trenches

An infiltration trench is a rectangular trench buried in the ground that is used to collect rainwater. It has a filter lining and is filled with a drainage material like well-washed crushed stone. It can also be equipped with a pump system.

The infiltration trench is usually connected to the house's downspouts. The rainwater is collected several metres away from the foundation, where it is absorbed into the soil or pumped into the sewer system.

Infiltration trenches can help reduce the volume of water that ends up in the sewer system when it rains heavily.

Floor drains

Floor drains are most often found in the basement (near the water heater) or in the garage. As their name implies, floor drains are installed in the floor to collect water in the event of a leak. The water then flows down to the sewer system.

Floor drains have a U-shaped pipe (siphon) where water collects and acts as a plug, blocking bad odours from the sewage system. However, over time, the water inside the siphon will evaporate. To avoid bad odours, it’s a good idea to add water regularly.

Flat roof drains

Flat roofs typically have a roof drain, also known as a gully. It's covered with a bell-shaped grate which prevents debris from blocking the drain. The water flows down the drain and reaches the sewer system through the home's plumbing system.

The grate should be kept clear at all times to prevent clogs, which could lead to a water buildup on the roof. As it freezes and melts, the water could seep into the home and cause water damage.


A ditch is a hole dug in a straight line with gently sloping sides (banks). It is used to drain, collect and/or circulate rainwater. The water is absorbed into the soil or flows to the sewer system.

Ditches are most commonly found on roadsides but some are located on private land. In many cases, they are part of the municipality’s drainage system.

The final word

A variety of systems are used to drain water and prevent seepage. The main ones are:

  • foundation drains, including French drains (terracotta, agricultural or BNQ) and interior foundation drains
  • linear drains
  • infiltration trenches
  • floor drains
  • flat roof drains
  • ditches

Now you can impress your clients with your new knowledge of residential drains!

By the way, if you're looking to relocate your policyholders after a disaster, why not take a look at our accommodations? With hundreds of postings all over Quebec, you’re sure to find what you’re looking for on our platform!

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