Frequently asked questions

Deep enough to sit below the water you are trying to catch, which usually means somewhere between eighteen inches and three feet. A drain laid a few inches under the sod intercepts almost nothing, and that is the most common reason a homeowner tells you french drains do not work.

A properly built drain with washed stone and fabric can run for decades. One built with the wrong stone, or with fabric wrapped only around the pipe, can silt up within a few years. The difference is entirely in the build, not the product.

The digging is straightforward. The slope is not. A run needs consistent fall along its whole length, and getting that wrong by an inch over thirty feet is the difference between a drain and a buried trough. Rent a laser level if you are attempting it.

Often, yes, and it is worth pricing both. Moving soil is usually less expensive per foot of problem solved than excavating a stone trench, and nothing buried means nothing to maintain.

The common figure is about six inches over the first ten feet. It does not need to be dramatic, it needs to be consistent and unbroken by a flower bed edge or a settled patch.

Sometimes on its own, often as the first and cheapest thing to try. If water is arriving at the foundation across the surface, stopping it at the surface is the direct fix.

It should not. A french drain is designed to take in groundwater slowly; a downspout delivers a surge. Combining them overwhelms the drain and pushes roof water into the soil you were trying to dry out. Keep the two systems separate.

As far as the ground allows, and further than most people assume. Ten feet is a common minimum, and on a flat lot with clay it needs to be more than that to actually help.

A hinged lid set flush in the lawn at the end of a buried line. Water pressure lifts it, the water leaves, and it closes again so you can mow over it. It is the usual answer where there is no bank to daylight the pipe.

A basin collects at one point, a channel drain collects along a line. Driveways, garage entries and patios usually need a line; a dip in a lawn usually needs a point.

Yes, and it is easy. Lift the grate, scoop out the leaves and grit sitting in the sump. Once or twice a year is normally enough, and skipping it is the reason most failed basins failed.

Usually yes, since both carry clean surface water in solid pipe. The line has to be sized for the combined flow rather than for whichever came first.

Mostly by elimination. If the roof water is being carried away, the grade falls away from the building, and water is still coming through at the base of the wall, the perimeter drain is the remaining suspect.

You are paying to dig along the foundation to the depth of the footing, by hand where access is tight, then to backfill and reinstate whatever was on top. The pipe itself is a rounding error in that number.

The cheaper alternatives are the three things that should be tried first: downspout lines, grading, and an exterior drain that intercepts water before it reaches the wall. They fix a lot of cases at a fraction of the cost.

Ordinarily the property owner, for the pipe serving their own entrance. What the road authority will and will not permit in the right of way varies, so it is worth asking the county or the city before the work rather than after.

It depends on how much ground drains to that point, and it is not a guess worth making. Undersized pipe is the most common reason a new culvert fails in its first big rain.

Frequently, yes, and that is always the first thing to check. A pipe that is structurally sound and merely silted is a cheap fix compared with replacing it.