How To Clean a French Drain

Surface Drain

Knowing how to clean a French drain may give you the ability to tackle the project yourself. It may also help you to determine if the situation requires a professional. A fully functional French drain is critical to keep your lawn dry. It will also help prevent water infiltration into the foundation or basement walls of your house.

A French drain is typically a perforated plastic pipe wrapped in a permeable landscape fabric and buried in a gravel-filled ditch. Ground water percolates through the gravel and enters the pipe. Once in the pipe, the water is taken away from the home’s perimeter or the place that the drain is protecting. French drains can empty into an underground gravel area, or in an aboveground gutter leading to the sewer. 

Here’s some information to help you identify and know how to clean a French drain.

Why Good Drains Go Bad

Over time, a French drain may become clogged. Tiny soil and clay granules slip through the pores of the landscape fabric and gradually build up inside the pipe. Another common cause of French drain clogs is root intrusion from grass, shrubs, and trees. Because the drain contains moisture, plant roots invade the pipe looking for water.

Signs of a Clog

You’ll know your French drain is clogged if you start seeing drainage problems that your drain was supposed to correct. Areas of the lawn may appear chronically soggy, or water may get in through your foundation or basement walls. You’ll see these symptoms during heavy rainfall, but not as much during dry spells when groundwater is reduced.

Doing It Yourself

There are a few things you can try if you don’t already know how to clean a French drain. Because most of the length of the drain pipe is buried, cleanouts that extend to the surface are often built into the pipe to allow access to segments of the span for removing clogs. To clear the pipe yourself, open a cleanout, insert a garden hose into the pipe, and turn the water on full force. To get as close as possible to the clog in the event there are multiple cleanouts, try flushing each one in sequence, beginning at the cleanout farthest from the discharge point. If the French drain discharges aboveground, you can also try flushing the pipe with the hose inserted at the point of discharge.

When to Call a Professional

If flushing with a hose doesn’t clear the clog, it’s probably time to call in a professional. Renting a powered drain snake like you’d use for indoor plumbing is usually not something DIYers should do. The perforations in the French drain pipe tend to interfere with the movement of the snake. This method should be left to professionals who have a specialized snake sized and previous experience using it.

The more desirable method professionals will use utilizes a water-jet system. A thin hose spraying high-pressure water is put through a head that is threaded into the underground drain pipe. The head incorporates several jets that emit knife-like streams of pressurized water strong enough to obliterate tree roots, accumulated dirt, and other naturally occurring blockages. The strong stream of injected water also flushes the disintegrated obstructions down and out of the pipe. These systems are typically used by plumbers and landscape contractors.

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