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This Drain Mistake Could Be Costly

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If you're here, you probably have a particular spot in your yard where water pools after a heavy rainstorm or when snow melts, leaving you with a swarm of mosquitos or a muddy mess. That, or excess moisture builds up in your soil and seeps into your basement, causing mold, water damage, and foundation concerns.

The solution to these types of water woes could be French drains, which might conjure up images of Parisian jardins or Baroque architecture but are actually named after their inventor, Henry Flagg French, who came up with the solution in 1859 to help drain water from farmland.

The drain system is simple in form: It's made up of trenches filled with gravel or rock that contain a perforated pipe that reroutes water away from problem areas.

"The drain operates by allowing water to flow into the trench, through the gravel and into the perforated pipe, which then carries the water away," explains Gene Caballero, owner of Your Green Pal, a site that connects homeowners with lawn service professionals.

A French drain system can be a cost-effective drainage solution for homeowners who face issues like water pooling in yards, basement dampness, or soil erosion, Caballero says.

Read on to learn everything you need to know about French drains, including whether you should add the hardscaping element to your own yard or basement and how to go about the process should you choose to have a contractor build one for you.

What Is a French Drain, and How Does It Work?

diagram of french drain system
Soumi Sarkar - Hearst Owned

A French drain is a trench that diverts water away from an area where it's pooling to a lower elevation where it can be released, explains Mike Arnold, director of The Gardens at Texas A&M University and a professor of landscape horticulture at its AgriLife Extension Service. A perforated pipe is placed at the bottom of the trench, Arnold explains, and the trench is then backfilled with porous materials like gravel or stone that help prevent the pipe from getting clogged with debris.

The drainage system works because water can move more efficiently through gravel than it can soil. Once water seeps into the drain, it's captured by the perforated pipe, which reroutes the water away from your lawn or your home's foundation and empties it into a more suitable place, like a sewer, storm drain, or drainage ditch (but definitely not into your neighbor's yard!).

A French drain differs from a trench drain because it's designed to manage underground water, whereas a trench drain is for collecting surface water, usually in paved areas.

The ideal situation for a French drain has a natural slope, which aids with water flow, Caballero says. Your drain should slope at least 1 inch for every 10 inches of pipe, which is considered a 1 percent grade.

Before you install a French drain, you need to check your local ordinances to determine whether the project requires a permit. You also need to locate any utilities, foundations, infrastructure, or major tree roots before you start digging, Arnold says. Contact your local power and water companies so they can mark any underground lines. If you don't already have a topographical survey of your property, you may need to contact an engineering firm to create one and confirm the slope is sufficient.

Benefits of French Drains

French drains can be an effective method for providing drainage to low areas in your yard that hold water following rain, irrigation runoff, and snow melt, Arnold says. "They're also an excellent way to enhance the drainage around trees or other planting areas in heavy clay soils," he adds. And since French drains are passive drainage mechanisms, they don't require a ton of maintenance.

Potential French Drain Mistakes

If your yard or basement doesn't have at least a 1 percent grade, a French drain may not be able to redirect the water effectively. Instead of flowing where you want it to go, the water might sit in the pipe and potentially create more drainage problems. A low slope is even more likely to cause a problem if you need to move the water a great distance, say, across your entire backyard to the closest storm drain. In that case, you might need to install a pump to move the water or consider a different type of drainage system.

You also need to be sure the place you're routing the water via a French drain can handle the additional water. If you're planning to send it into a municipal storm drain that's on your property, be sure that storm drain isn't constantly clogged or already overwhelmed by water from other areas.

Should You DIY a French Drain or Hire a Contractor?

Small-scale French drains could be reasonable DIY projects, but moving large volumes of soil and backfill can quickly become hard work, Arnold says. A skilled contractor can bring expertise and construction equipment, like a trench digger, that are needed to dig and grade the soil; they can also assist with the permitting process, coordinate with your utility company, solve any design issues, source the materials, and remove the excess dirt they dig up, he adds.

How Much Do French Drains Cost?

French drain installation typically costs between $500 and $18,000, depending on the scope of the project. The national average cost of French drains is $9,250, according to Angi, a service that connects users with home and landscaping pros. Specifically, yard trench drains cost about $30 to $90 per linear foot, per Angi.

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