French Drain: Definition & Installation Process

French draining

Do you have trouble with groundwater or poor drainage in the backyard? Then, you’ve come to the right place because we have an effective solution. A French drain can help you transfer water away from your property and it’s actually relatively easy to build one in the yard yourself.

But first, let’s explore further the specifics and purpose of a french drainage system. Read on!

What exactly is a French drain?

Тhe main purpose of french drains is to collect surface water and groundwaters and divert it away from the foundation of your home to prevent moisture seeping into the house. They are usually set up simultaneously as a new house foundation is built if the area is known to have an abundance of groundwater.

French drains can be installed both around the foundations or under the basement. The second is usually done when moisture is expected to creep into the house through the basement floor. The pipes laid under the basement capture the water before it reaches the foundation and leads it away.

French drains, which are often called weeping tiles too, were originally trenches filled with rocks or gravel to divert water by providing it with a path of least resistance. French drains do not come from France but were invented in the sunset years of the 19th century by the American lawyer Henry Flagg French who apparently was also an avid farmer. The first designs didn’t feature a pipe at all, but instead, roof tiles arranged peculiarly. Needless to say, the modern designs are not at all as prone to being clogged with soil and roots.

Nowadays, french drains are built with a pipe perforated on the bottom to increase the volume of water that can flow through them. This gets rid of soil clogging up the space between the rocks the original design has. Landscape fabric is also used to protect against this, making it possible to grow turf above the french drain.

Alternatively, weeping tiles can be used to:

  • Improve the drainage of your garden in an efficient and inconspicuous way.
  • Relieve pressure on retaining walls caused by groundwater.
  • Lead water away from roads and driveways

French drain variations

In order to make the best choice for your garden, it’s also good to explore the different French drain variations out there and their specifics.

  • Curtain drain – This variation is what we mention earlier. While the traditional French drain is open so water can use a perforated pipe surrounded by gravel. This variation is similar to the traditional French drain, the difference being that the traditional is open so water can clearly flow into the gravel. The curtain drain has a lair of soil atop that can be used for turf or planting.
  • Collector drain – It combines groundwater drains and surface water runoff. Filters must be installed on the drains that collect surface water to prevent the underground pipes from clogging. This is an efficient way to quickly divert rainfall or any water runoff from the surface to underground plumbing.
  • Fin drain – The drainpipe has a fin extending above it. The fin is made of draining composite and sucks up moisture from the ground, delivering it to the pipe it extends from. These are the most advanced types of french drains and are actually cheaper to build as both the pipe and the fin cannot be clogged by soil, and thus the need for backfill material is reduced. This naturally saves both time and money when building the drain.

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How to install a french drain (DIY)

Important steps before you start:

  • Check if the law allows such a project to be done in your backyard and the appropriate channels to run it through. It may be annoying to deal with bureaucracy sometimes, but it’s worth doing the right way.
  • Ensure there are no running power lines or piping through the spot where you’ll be digging. Once again, consult the municipality.
  • Consider whether your french drain will be bothersome for your neighbours. Groundwater runoff in another person’s property can give them grounds for legal action against you. Ideally, you want to choose a runoff area away from any buildings and private property.
  • Find an incline. For the drain to work, the piping should be sloping at a 1° angle. If there is no natural sloping, you can create an artificial one by gradually digging deeper. This can be done by planting down stakes along the drain path and the length of the rope between them. Then using a string level, gauge the incline. If you are not sure how to do this yourself, it’s best to hire a professional surveyor.

Needed tools and materials

Supplies needed for a french drain
  • Shovel – This, of course, is the bare minimum, and it may be backbreaking labour digging the entire trench by hand. However, it’s also free. Fees for a backhoe and an operator for it can cut deep into your budget.
  • Gravel – The gravel you use for the project must be washed. The tiny particles sticking to it may end up in the drain pipe.
  • Perforated pipe – The size of the pipe will vary depending on how severe the drainage problem is. There are flexible varieties too, but their durability is lower, and they tend to be more difficult to unclog should the need arise.
  • Landscaping fabric – It will keep soil, roots, and other small debris from clogging up the pipe. There are specialised pipes that come with a landscape fabric “sock” built up into the design.

Step 1 – Dig up the trench

Dig a trench.

Start by digging a trench for the french drain. The size is not set in stone and can vary depending on the functionаlity you have in mind.

A deeper trench would work best for groundwater draining, while rainwater will drain more easily if the drain is closer to the surface. Ensure the trench does not have any grooves and bumps as these will cause water to pool in them and prevent the proper drainage.

Step 2 – Line with landscaping fabric

Line the trench with landscaping fabric.

The landscaping fabric will permit water to go through it but will prevent any soil and small particles to be washed into the drain’s holes. If the particles get into the drain and reach the pipes, they may clog them.

This is an important step and we recommend using a high-quality fabric, which will last longer.

Step 3 – Put down a gravel bed

Gravel bed for the french drain.

Shovel around 5 centimeters of gravel on top of the landscaping fabric to prepare the pipe’s “bed”.

Step 4 – Lay the pipe

Lay down the pipe.

The pipe’s holes must be pointing down. This may seem counter-intuitive at first, but this is the way to make it work best. If they are pointing up, some of the water will get into them, but most of it will pool beneath the pipe. Water always chooses the path of least resistance, and what your French drain does is to provide one for it. The water will “climb” through the holes of the pipe and follow it to the runoff spot.

There are different types of pipes, some of them punctured all around the pipes’ diameter. Consult the hardware store assistants to find out which one is best for you.

Step 5 –  Fill in gravel

Wrap the fabric around.

Shovel the gravel over the pipe until it almost fills the trench. It’s important to leave some space to fill soil back in. Then, unpin the landscaping fabric and wrap it around. This way, you ensure the french drain is protected from small particles from all sides.

Step 6 – Final touches

finishing touches

Now, you can choose what to do with the remaining space. You can either fill up with gravel, which will make rainwater draining easier or fill it back up with soil and plant turf over it. 

The point of wrapping the drain with landscape fabric is to minimize future French drain maintenance and ensure you won’t have to change piping for at least a few years. This also means that if you choose to plant turf above the drainage system, it won’t be disturbed for quite some time.

Get professionals to deal with the French drain installation in your backyard! Contact us with the details.

French drain maintenance tips

While such a drainage system does not require a lot of maintenance once installed correctly, it’s still good to keep the following in mind:

  • Regularly check for signs of damage or clogging.
  • Pay attention to the condition of the soil, as well as the runoff spot for debris and leaves collection.
  • Cleaning, repairs or pipe replacement may still be necessary at certain point. French drains are most often cleaned with the help of an elexctric sewer snake. As for repairs and more serious work, digging up the trench again will most likely be necessary. While inconvenient, it is essential to do it for the effectiveness of your dainage system, especially when it helps protect your home’s foundation from groundwater.

Takeaways

  • French drains help collect and transfer groundwater, as well as surface water away from your property.
  • Laying a French drain by yourself is doable, but be prepared for some digging and a bit of messy work.
  • Before you start the installation process, it is important to check the laws in your area for whether you are permitted to build such drain in your backyard.
  • It’s also good to investigate whether the project will affect already established pipes or power lines, as well as your neighbours and their property.
  • French drains are low-maintenance, so an occasional cleaning should be sufficient and will not take a lot of time. Repairs, on the other hand, will be a bit more time-consuming.
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