What is a french drain and how do you install one?

French drains are a type of drain that are used to remove excess water from the ground in your section or garden.

They’re very useful when you want to make sure that the ground doesn’t become water logged and stop you from being able to plant anything.

This is especially useful if you live in an area where there are heavy downpours or periods of torrential rain.

French drains are one of the easiest ways to get rid of water in your yard. They’re cheap, easy to install, and don’t require a lot of maintenance.

If you want to learn how to make a french drain in your garden, then keep reading.

What are french drains?

A French drain is a trench filled with gravel or rock, or both, containing a perforated pipe that redirects surface water and groundwater away from your house foundations.

French drains are typically installed to help prevent flooding or prevent water damage to your house.

How do they work?

French drains help carry ground-water away from your foundation when you have water-table problems.

Water runs into a gravel-filled trench, then into perforated pipe at the bottom of the trench.

The water then travels through the pipe and is then emptied a safe distance from your house.

Installing a french drain

Before you get started on your french drain, check the laws in your area for the exact requirements for such a job. Make sure there are no power lines, cables, or pipes under where you’ll be digging.

Step 1: Decide on the route

Achieving the proper 1-degree slope will help your french drain work effectively. To do this, you can create an artificial slope by gradually digging deeper along the path of your French Drain, or preferably find a natural incline.

Next, you’ll need to decide on a runoff area. It’s important that you don’t put your french drain in a place where it will overflow into anyone else’s property. Think about what will happen when it rains and the water fills up the french drain. Where is it going to go?

Talk to neighbours to let them know that you are planning on creating a french drain on your property. Ask them if they have any concerns with regard to the project. Address these concerns as best you can.

Step 2: Dig a trench

The first step in installing a french drain is to dig a trench along the outside perimeter of the basement wall.

Make sure that the trench slopes slightly away from the house so that water will move away from the foundation. The trench should be about one foot deep and wide enough to fit a PVC pipe at the bottom of it.

Step 3: Add gravel

Gravel will provide support for the drain pipe and allow water to flow freely through it. The gravel should be about 8 inches deep, with an additional inch of pea gravel added on top of the PVC pipe.

Step 4: Place filter fabric

Place filter fabric over the gravel before adding more dirt. This will prevent soil from clogging up your drain pipe, which would render its use useless. You can buy filter fabric at your local hardware store for about $20 per roll.

Step 5: Add more dirt

Cover up your french drain using more soil dug up from the trench. Make sure that you add enough

How deep should a French drain be?

If you’re dealing with pooling water on the surface of your property, your best bet is a shallow trench. If you’re trying to stop water from getting into your basement, you may need a deeper French drain.

Your French drain should be at least 45cm deep, but you generally won’t need to go more than 60cm. The pipe needs to be this deep so it will capture most of the excess water.

If you want to protect your foundation or keep water from getting into the basement, you’ll want to install your drain pipe deep enough to do that.

If you have a concrete slab foundation, you’ll want your drain installed below the level of the slab, or about 0.5m down.

When you need a french drain

Here are the key circumstances when you should build a french drain:

  1. If you have standing water, or if the ground slopes towards your house and you’re having problems with water seeping under your house.
  2. If you want to prevent a future problem. For example, if your neighbour expands their house or garage, and the construction causes water to start pooling in your yard.
  3. If the rest of your yard is fine, and you just need to improve drainage in one area.

An alternative is building a rain garden instead of a french drain. Rain gardens are designed specifically for handling surface drainage problems and they look nicer than french drains. However, they require specialized knowledge and are harder to install properly than french drains.

French Drain from Bunnings

Bunnings stock slotted Agi Pipe that could be used to build a french drain. The other products required should also be available at your local Bunnings.

Summary and takeaways

In the end, French drains are a cost-effective way of dealing with areas that tend to have problems with water.

They are usually easy to install and you hopefully won’t need to remove any walls or other hard landscaping features.