How often should you flush a French drain?
Updated July 2026
Flush or jet a French drain every 1 to 3 years, moving toward the yearly end if you have silty soil, iron in the groundwater, or mature trees within reach of the pipe. A French drain is just a perforated pipe in gravel, and it only works while water can flow through it. Silt, roots, and mineral slime slowly pack the perforations and the pipe until it stops draining. When that happens, the wet basement or soggy yard the drain was built to protect simply floods again.
What changes the interval
| Your situation | Interval | Why |
|---|---|---|
| Sandy, well-draining soil | Every 3 years | Little fine sediment to migrate into the pipe |
| Silty or clay soil | Every 1–2 years | Fines wash in and pack the gravel and perforations |
| Mature trees within 20 feet | Yearly, and camera it | Roots seek the water and invade the pipe joints |
| Iron-rich groundwater (ochre) | Yearly | Orange iron-bacteria slime clogs perforations fast |
| No filter fabric on the pipe | More often | Nothing keeps soil out, so it silts up quickly |
| After a very wet season | Test the flow | Heavy flow can move a season of sediment at once |
The cost of skipping it
What skipping it costs: a drain nobody flushes is a drain that quietly fails, and you usually find out during the storm you needed it for. The bills climb from there: a flooded finished basement is $3,000–10,000 in cleanup and drywall, a failed exterior drain that has to be dug up and replaced is $5,000–15,000, and chronic wall seepage can drive foundation work. A routine hydro-jet flush is $200 to $600, and a camera inspection to see what is happening inside is often $150 to $350.
How to do it (DIY hose flush, or $200–600 for a pro hydro-jet)
- Find both ends: the cleanout or inlet and the outlet where the drain daylights or ties in.
- At the outlet, check for a weak trickle or no flow during or after rain, the classic clog sign.
- Feed a garden hose into the cleanout and run it wide open to push loose sediment toward the outlet.
- For a real clog, rent or hire a sewer jetter, which drives a high-pressure nozzle through the pipe.
- If flow does not return, run a drain camera to locate root intrusion, a crushed section, or a silted run.
Knowing the interval is the easy half. OnOtto reminds you at the right interval, and it won't let you snooze it into next year. Tasks persist until they're done, and completing French drain flushing schedules the next one automatically.
Put this on autopilot, free for 30 daysFrequently asked questions
How do I know if my French drain is clogged?
The tells are all about water not going where it used to. Puddles linger over the drain line or against the foundation after rain, the outlet that once gushed now trickles or stays dry during a downpour, and a basement or crawlspace that had been dry starts weeping again. Slow-draining soil and a spongy lawn along the trench are earlier hints. If the outlet runs weak while water is clearly pooling upstream, the pipe is packed and needs flushing.
Can I flush a French drain myself?
A light maintenance flush, yes: feed a garden hose into the cleanout and let it run to push out loose silt, ideally once a year before the wet season. What you cannot do with a hose is clear a real clog of packed sediment, roots, or iron slime. That takes a sewer jetter (rentable, but easy to misuse) or a pro with a jetting rig and a camera. If a hose flush does not restore strong outlet flow, stop and call someone before you back water up into the line.
What clogs a French drain in the first place?
Three things, mostly. Fine silt and clay wash in through the gravel and pack the pipe perforations, which is why filter fabric matters and why silty soils clog fastest. Tree and shrub roots hunt for the water and grow in through joints and holes. And where the groundwater is iron-rich, iron bacteria form a rusty orange slime (ochre) that cements the perforations shut. Trees within about 20 feet and a pipe with no filter fabric are the two biggest risk factors.
How long should a French drain last if I maintain it?
A properly built drain, with the pipe wrapped in filter fabric and set in clean gravel, can last 30 to 40 years when it is flushed on schedule. Skip maintenance and that can drop to under 10 as silt and roots take over. The single biggest lifespan factor is whether it was built with filter fabric and the right gravel in the first place. Learn what a good one looks like in what is a French drain.