French drain installation: How to prevent water damage in your basement
A French drain is the perfect foil for water pooling in your yard. Best of all, they can be relatively straightforward to install for DIY jobs — here's how.
Our experts independently review everything we recommend. If you buy through our links, we may earn commission.
Installing a French drain is one of the simplest ways to prevent water from pooling in low spots in your yard or near your home's foundation. Not only is that important for keeping your yard looking nice, but it also prevents water damage in your basement from becoming a problem by redirecting water where you want it to go. In some cases, you can install one in your basement if water seeping in is still problematic.
But what goes into a French drain installation? And can you install one yourself? Here's what you need to know.
What is a French drain?
A waterlogged yard with standing water due to poor drainage
A French drain is a relatively simple system for directing water where you want it to go in your yard or basement. While the name may lead you to believe they're a French invention, the system gets its name from Henry French, a Massachusetts judge and farmer who used the drain system to prevent farmland from becoming waterlogged in the 19th century, according to Drycrete Waterproofing , a Rhode Island-based waterproofing company. You may also see them referred to as a perimeter drain or foundation drain, among several other names, Drycrete says.
French drains are made up of a perforated pipe placed in a trench that empties water into a designated drainage area. The trench is filled with porous material, like gravel, to allow water to reach the pipe. As water seeps into the ground, it enters the pipe and is directed wherever the drain empties. In some cases, you may also have an inlet basin (also called a catch basin) to catch surface water where it pools.
Outdoor French drains are a relatively straightforward DIY job you can complete with proper planning. However, interior French drains may involve breaking up concrete around the edge of your basement and require more professional expertise (along with a sump pump). You're better off hiring a plumber or waterproofing company for an interior French drain system to avoid costly damage.
How much do French drains cost?
The cost of installing a French drain varies a lot depending on how long it is, complications in your yard and whether you're putting one in your basement or outside. The typical cost ranges from $500 at the low end to $18,000 at the high end, according to local service review and recommendation site Angi . The average cost is around $9,250 if you hire a professional to do the work.
You can save thousands if you have relatively simple needs and go the DIY route. Angi estimates you can install a DIY French drain for under $1,000. However, it's important to be realistic with the scope of the job and consult a professional if you aren't sure what you're doing.
Note that you may also need a permit to install a French drain, depending on your location. Speak with your local building department to inquire whether one is required. Permits typically cost between $50 and $200, Angi says.
What materials do you need to install a French drain?
A trench dug through a yard in preparation for installing a French drain
The materials you need to build a French drain are easily accessible at your local hardware store. Here's a look.
Shovel
Any spade shovel will work for digging your trench, but you'll have a much easier time with one like this trenching shovel from Home Depot .
Perforated pipe
Ideally, you should use a pipe at least four inches in diameter. The most common option is a black, corrugated, perforated pipe like this one from Home Depot , which comes in lengths from eight to 50 feet starting at $6. Alternatively, you can use a more durable perforated PVC pipe, though it's much more expensive at nearly $20 for a 10-foot section .
Landscaping fabric
This is what will line your trench and wrap your pipe, preventing dirt and debris from infiltrating the drainage system. You can use any landscaping fabric, though this 150-foot roll of soil separator fabric is a cost-effective option.
Gravel
Bags of gravel or drainage rock are relatively inexpensive and easy to find at your local hardware or gardening store for around $5 for 50 pounds . Don't worry about spending a lot on pretty rocks; these will be buried in your trench.
Inlet basin/catch basin (optional)
If you're just running a French drain along a low point in your yard, you don't necessarily need a catch basin. However, they're very handy for placing at a point where water typically pools, allowing it to flow into a wide opening before entering your pipe. They're also relatively inexpensive, starting at around $15 at Home Depot .
How to install a French drain
Pipe in the process of being laid in a trench in the ground
Building your French drain is relatively straightforward, but you should pay extra attention to some particular aspects of the job. These include the location of your drain pipe, the depth of your trench, the pitch of the pipe and the location of any utility or electrical lines. Here's how to get started:
1) Choose your location
This is the most important step of installing a French drain, so you want to get it right. Look at where water is pooling, either in a low spot in your yard or near your home's foundation. The goal is to go from this area to your outlet, preferably near a storm drain or street.
Avoid draining your pipe into a neighbor's property, near buildings or anywhere the water may cause damage. Also, call 811 to ensure you know exactly where gas and sewer lines or electrical wires are in your yard before you start your project. You shouldn't install your pipe near any underground utility lines.
Finally, if you determine the length of your French drain is more than 50 feet, you may want to call in a professional instead, home improvement site Bobvila.com says. While DIY drains are doable under 50 feet, they become more complicated the longer they are.
2) Dig the trench
Whether you're directing water away from your home or a low spot further away in your yard, you start by digging a trench. Home Depot recommends digging your trench around 18 inches deep and between nine and 12 inches wide. Additionally, you want to ensure the pipe you install later slopes downward at least one inch for every 10 feet of pipe to keep water flowing properly.
Again, ensure you aren't digging near any utility or electrical lines to stay safe. If digging a long trench, take plenty of breaks and stay hydrated. Digging for any length of time can be backbreaking work, after all.
3) Line your trench
Once you have your trench, it's time to start lining it with your landscaping fabric. This acts as an additional barrier to prevent dirt and other debris from entering and clogging the pipe. Line the bottom of the trench with the landscaping fabric, leaving about 10 inches of excess fabric on each side.
Once your landscaping fabric is laid, create a layer of gravel on top of it. General guidance, including from Home Depot and HGTV , is to create a layer roughly three inches deep throughout the length of the trench. This creates another layer to filter water and your pipe will sit on top of it.
4) Install the pipe
Lay the perforated pipe through your trench. Connect sections of the pipe until you have an adequate length to make it from the start of your trench to your drainage point. Be sure to keep the drainage holes pointed downward throughout the length of the pipe.
Once connected, you can lay the pipe in the trench and test it by running water through it. If necessary, this is also when you should install your inlet grate. If water flows easily through the pipe, you can proceed to the next step.
5) Add gravel
Add an additional layer of gravel on top of the pipe for the length of the trench. This acts as another layer to filter water entering from above and keep water moving.
6) Wrap the gravel and pipe
After you've covered the pipe with gravel, use the excess landscaping fabric you left on the sides of the trench. Wrap the gravel and pipe like a burrito, tucking the excess fabric on the sides. Again, the fabric helps prevent dirt and other small debris from infiltrating the pipe and causing clogs.
7) Fill the trench and test once more
Finally, you can fill the rest of the trench with the dirt you dug out earlier to cover the length of the pipe. Once completely covered, test the pipe again by running water through it to ensure there are no issues.
Should you go with corrugated or PVC pipe?
The drain end of a corrugated black pipe
The choice of corrugated pipe or perforated PVC pipe with holes depends on the path of your trench and your budget. Black corrugated piping is used in many drainage systems and is valued for being flexible and affordable. However, its thin walls are more susceptible to damage, and dirt can easily get caught in its ridges, raising the risk of clogs.
On the other hand, PVC pipe is durable and smooth, making it much more resistant to damage and clogs. It's also available in many sizes and will likely last longer than its thinner, corrugated cousin. Unfortunately, it's inflexible and more expensive, making it a tough sell for very long or curved runs.
According to Commercial Industrial Supply , a South Carolina-based company that sells pipes, fittings and other industrial products, the typical route for French drains is black corrugated pipe. It's more affordable and its flexibility makes it a good choice if you have slight curves in your trench. However, if you have a relatively simple, straight line to your drainage point and can afford it, PVC will last much longer and is less susceptible to damage and clogs.
Keeping your French drain going
The inside of old water drainage pipes, showing why it's important to stay on top of upkeep
While a French drain can be a relatively simple DIY project for short runs, it still requires regular upkeep to keep working at its best. To ensure the pipe is clear of clogs, check the water flow regularly, especially during heavy rains. If you have an inlet grate, keep it free of dirt and debris to prevent debris from falling into the pipe.
You should also occasionally check the pipe for damage from roots, which can penetrate it over time. That's especially true if you use black corrugated pipe, which has thin walls that may be more easily broken. Finally, if you notice the water flow has slowed down, clear any clogs with a drain snake and flush it with water.
Have more DIY plumbing projects on your checklist? Read our guide to the best DIY plumbing tools for homeowners to stock up on what you'll need. Thinking of hiring a plumber instead? Check out our guide to the most common plumbing problems and how much they cost to fix.
