How To Install A French Drainage System

How To Install A French Drainage System

Are you looking for a foolproof way to protect your home from flooding? Are you considering building a French drainage system but need help figuring out how to start?

A French drain is a type of in-ground drainage system that utilizes underground pipes and trenches filled with gravel to redirect water away from a particular area. This is crucial because of all the ways that poor drainage can damage your lawn.

Installing a French drain requires some digging and manual labor, but it’s not as difficult as you might think.

In this guide, we’ll show you how to install a French drainage system in 9 steps.

By the end of this article, you will know how to install your own French drainage system quickly and efficiently without having any prior experience or knowledge of drainage systems.

But if you’re looking to optimize the watering of your lawn, you may need a professional irrigation installation and design.

*Before we get started, don’t forget to call 811! It’s important that you are aware of any potential underground utility lines so that you don’t accidentally damage them during installation. 

1. Design The Layout

The first step in installing a French drain is designing the layout for your particular project. This means figuring out where the water is pooling and where you want it to go. 

Once you know these two things, you can decide where the drain should go, what type of pipe to use, and where to divert the runoff water.

Remember that in order for a French drainage system to work properly, you must be moving water from a higher elevation and draining to a lower elevation. But should you connect your system to a drain?

Depending on local regulations, you may be able to connect your system to a sewer drain, although we don’t recommend that method.

After you’ve decided where you want the water to drain, outline your drainage system with marking paint, stakes, or flags. 

2. Dig The Trench

Dig a trench from where you want to move water to the location where it will output. The size of your trench will depend on the size of your pipe, but you want to make sure that you dig deep enough so that you can add the pipe and a few inches of gravel but still have enough space to cover it with a few inches of soil and gravel on top. In general, aim for a depth between 18 and 24 inches.

Also, remember that you need the trench to slope towards the outlet. We recommend sloping 1 inch for every 10 feet of trench.

3. Add Gravel To The Trench

Add about 3 inches of gravel to the trench that has been dug out for your French drain. Gravel helps keep soil from entering into the drainage pipe while also allowing for maximum water flow throughout the entire length of the pipe being used in your project. The gravel also functions as a solid bed for the pipe to rest on.

4. Wrap The Pipe In Filter Fabric

You have several options when it comes to piping for your French drainage system. You can use a flexible drain pipe with perforations, or you can use a rigid PVC pipe with holes in it. Both options work well, but rigid PVC will last longer.

Wrap the perforated pipe (also known as field tile) in filter fabric. This will allow water to enter the perforated pipe while simultaneously preventing any soil or gravel from entering.

5. Attach The Pipe Connections

Once gravel has been added to the trench dug out for your project, it’s time to attach all necessary piping connections together before placing them inside the trench being used for drainage purposes. This includes attaching an inlet grate to the pipe in the area where you want to drain water away.

Use Root Ban for any connections you need to glue together.

Make sure that all piping connections are secure before moving on to the next step. 

6. Place Pipe Drain In The Trench

Lay your connected pipe structure in the trench, taking care to orient the pipe holes toward the bottom of the trench. Make sure the filter fabric is still completely wrapped around the pipe.

7. Cover The Pipe With Gravel 

Once you have placed the perforated drain pipe and all the connections inside the trench, it’s time to cover it all up with gravel. Remember to leave enough space for you to backfill the trench up to ground level.

8. Backfill The Trench

Use the excavated soil from your trench to cover up the gravel, piping, and filter fabric. Take care not to spill any soil into your inlet grate. We recommend covering it with a piece of cardboard while you complete this step.

9. Maintain As Needed

If necessary, reseed the soil on top of the trench or add other types of landscaping material if desired (landscaping stone, etc.). For maintenance, you’ll want to regularly inspect the inlet grate and drainage outlet to ensure they don’t get clogged.

If your drainage system gets a blockage, try flushing it out with a garden hose. For PVC pipe installations, you can use a plumber’s snake.

Connecting Your French Drain To A Municipal Storm Drain (Optional)

If you have a municipal storm drain nearby, you may be able to attach your French drain outlet to it. However, keep in mind that many municipalities require you to get a permit for this option. If you hire a professional team like the drainage experts at Simmons Landscape & Irrigation, they will handle the permitting.

Once you have the proper permit, you can dig around the municipal storm drain to see if there is an intake sleeve that you can connect to your French drain. If it does, simply use the proper size adapter to connect the end of your drain line to the intake sleeve.

If the municipal storm drain lacks an intake sleeve, you will likely need to hire a professional who can drill a hole and install an intake sleeve into the municipal system.

Installing A Gravel-Less French Drainage System

While the traditional method for French drain installation involves adding gravel and wrapping the drain pipe in filter fabric, there are new products that allow you to install a gravel-less version of the French drain system. You can purchase a corrugated drain pipe that is pre-wrapped in filter fabric with several inches of expanded polystyrene pellets between the filter fabric and the pipe.

To install this type of system, follow the same instructions above, but skip the steps that involve wrapping the pipe in filter fabric or adding gravel to the trench. The polystyrene pellets will function as the gravel, so it’s simply a matter of digging the appropriately sloped trenches and connecting the drain pipe to the system outlet.

Pro Tips For Installing French Drains

• For additional draining capacity, try digging a 3’x3’x3′ pit at the end of the French drain pipe and filling it with rocks.

• Alternatively, you can add a catch basin or underground cistern at the end of your French drain pipe if you want to reclaim the water and use it for your garden.

• We recommend placing some type of marker (a flag or a distinctive rock) at the drainage outlet so you can easily find it and actively keep it clear of blockages. 

• You will likely have extra soil left over after you have backfilled your trenches. Make sure you have a plan for what to do with this excess soil.

Advantages Of French Drains

The primary advantage of French drain systems is that they are an effective way of dealing with excess water at the ground level. In the same way that your roof’s gutter system is an effective system for moving water off of your roof, a French drainage system is an effective way to remove excess water at the ground level of your property. If you have water pooling at a low spot in your yard, a French drainage system is likely the best solution for that issue.

Another advantage of French drains is their ability to alleviate flooding issues around foundations or basements. Since French drainage systems are a type of in-ground drainage system, they are able to route water away from a home’s foundation or basement walls more effectively than almost any other type of drainage system.

When NOT To Install A French Drainage System

While French drains are great for most homes, there are some situations when they may not be suitable for yours. If you have a “fishbowl” yard that slopes significantly toward your house, or if you live in an area with high groundwater levels, then you should consider another type of drainage system instead, as these conditions can affect how effective a French drain will be at diverting water away from your property. 

Simmons Landscape & Irrigation Can Install Your French Drainage System

We hope the steps outlined above have given you a good idea of what’s involved in installing a French drainage system. If you’re unsure about any part of the process or just want a professional team of experts to handle the installation for you, we can help!

Just give us a call or fill out our contact form today. We’ll be happy to assess your situation and help you find the best solution for your needs.