What Is A French Drain and How Does It Work?

This article will discuss what french drainage is all about and how it works. You’ll have answers on whether this drainage system will solve your flooding issues as you read on.

We also discuss the two types of french drains and how to install this drainage system.

What Is A French Drain System, And How Does It Function?

Simply put, a French drain helps collect and redirect water. Its design consists of a wide perforated pipe laid on the ground and covered with porous sand, gravel, or rock materials.

To make such a drain efficiently direct water away, it must be angled downwards away from the area where water collects.

SEE: Interior French Drain Pros And Cons

Why Is It Called A French Drain?

Unlike what it sounds, French drains didn’t originate from France but got their name from their founder Henry French. Surprisingly, he wasn’t a plumber but a Judge.

The scientist first promoted his drain idea in a book about farm drainage in the mid-19th century.

Since then, the idea has become highly efficient in fixing flooding-related problems. This drainage system consists of wide perforated pipes placed in the ground and covered with porous materials.

They’re angled downward to help collect and convey water away from affected areas.

Water collected can be diverted to many places, including a low-lying section of your property, the street, a drainage ditch, or a dry well. The objective is to move water from vulnerable areas to other locations where minor damage will result.

French drains are often located in several areas, such as near retaining and foundation walls. This positioning is prominent; it helps prevent groundswell pressure caused by water accumulation during rainfall.

Types of French Drains

There are two types of French drains; the collector & interceptor drains and the curtain drains.

So, what are the differences between these two, and what uses does each serve? In answering the latter, it’s evident that both serve the purpose of resolving water accumulation or flooding.

A collector & interceptor drain is a French drain that helps move ground and surface water into the drain for onward disposal. It’s most ideal when you need to address both surface runoff water and groundwater issues.

A filter is needed to prevent soils from washing into the perforated French drain pipe in the ground.

On the other hand, the Curtain drain is a French drain type that is easy to maintain and manage. It requires only perforated pipes placed along the depressed ground and covered with gravel.

Curtain French drains are commonly known as traditional French drains.

How A French Drain Works

First off, French drains are ideal when water is getting into your basement, when dealing with a driveway washout, or when your lawn often turns soggy after a downpour.

Also, French drains serve your water draining needs when constructing a retaining wall.

These drains are gravel-filled trenches with perforated pipes that help convey water that collects into it. Porous materials (gravels, sand, or rocks used) help with the easy flow and collection of water into the trench.

As water flows through the rocks and soil, they pass through the pipe perforations and drift away from your home. A French drain needs to be correctly installed to ensure proper water disposal.

It’s best to have a pro handle your drain installation.

For best results, the trench bottom should be angled at about an inch for every 8 feet towards the direction you wish the water to flow. Your installer will recommend where to have such water flow.

DIY Installation of French Drains

While it’s best to have a pro handle your installation needs to avoid french drain mistakes, sometimes you may want to try your hands on the project.

There shouldn’t be any issues if you do proper research on the procedure. It will also help if you’re technically inclined or have handled similar jobs in the past.

Whatever the case is, there are basic guidelines to follow to have your French drain adequately installed. First, it needs proper calculations; the placement of your pipes is vital.

Also, the suitable piping material is essential to obtaining the right results and ensuring your drain works for a long time.

What more? It would be best to be attentive to other installations like gas and plumbing lines around the area. Let’s briefly discuss each of these points, shall we?

  • Proper Calculations are Vital

The installation process of French drains isn’t haphazard.

There needs to be a proper understanding of how water dispersal will play out. You want to have a situation where water drains out as quickly as possible and doesn’t cause a delay in filling the pipe.

  • Pipe Placement should be Done Right.

How your drainage pipes are placed matters a lot. Perforated sections of your lines should face upwards and not downwards. Putting it the wrong way defeats the goal.

Aside from the drainage pipes, you should use only suitable porous materials. The focus here is that such materials should be absorbent enough.

You might want to get the right kind of stones to avoid clogs. Some professional advice might be of help. You can watch online videos of successful installation procedures on YouTube and the types of materials used.

  • Only the right Kind of Pipe will Serve

Not all pipes will work for a French drain.

While some may offer temporary relief, issues might soon result from inefficient water draining. With the wrong type of pipework, you may need to have them replaced after a while.

This is unnecessary and adds to the cost of installation.

  • Pay Attention to Other Installations Around

When installing a French drain, paying close attention to other installations like gas and plumbing lines is essential. This action helps prevent damage that could be expensive to fix.

These areas need to be mapped out to understand what lies beneath.

With the information, you should have a better idea of a French drain. More importantly, we’ve discussed how this works and the procedures for its installation.

1 thought on “What Is A French Drain and How Does It Work?”

  1. It’s great that you mentioned how a French drain helps collect and redirect water. I was reading a book about drainage systems earlier and I learned about French drains for the first time. According to what I’ve read, it seems professional French drain repair services are available now too.


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