French Drains & Downspout Lines in Knoxville, TN

French drains and downspout lines solve the most common drainage problem around Knoxville: water that sits in the yard or runs against the house after one of the region's heavy rains. A French drain is a trench with perforated pipe wrapped in clean stone that collects groundwater and surface water and carries it to an outlet. A downspout line is a solid pipe that takes roof water from the gutters and releases it well away from the foundation. Many yards need both.

Why clay lots stay wet

Knoxville gets just under 52 inches of precipitation a year, much of it in hard downpours. The red clay subsoils common here, like Dewey and Talbott, are slow to absorb water, so rain runs across the surface or perches on top of the clay. A yard that drains well in a light rain can turn into a pond in a thunderstorm. Crawlspaces on the uphill side of a lot take the worst of it.

How we build a French drain

We dig the trench with a steady fall toward the outlet, line it with filter fabric where the soil calls for it, lay perforated pipe on a bed of washed stone, cover it with more stone and finish with fabric and topsoil or more stone at the surface. Curtain drains go uphill of the area to protect, catching water before it reaches the house. Footing drains along a foundation are usually part of a waterproofing or new construction job.

The outlet matters more than the pipe

A French drain is only as good as where it ends. Good outlets are a curb or ditch at a lower elevation, a pop-up emitter in a stable part of the lawn, or a designed dry well where soils allow. In karst ground, one outlet is off limits: a sinkhole or depression. Adding concentrated water to a sink can enlarge it or start a new collapse, so we never route a drain into one. If there is no legal outlet on your lot, we tell you so before you spend money.

Downspout lines

Many gutters dump water right beside the foundation. Burying the downspouts in solid pipe and carrying the water 10 feet or more away, to a pop-up or into a French drain outlet, is one of the cheapest drainage fixes. We install cleanouts so the lines can be flushed.

What it costs

HomeGuide lists exterior French drains at $10 to $35 per linear foot, with a typical 100-foot run around $1,000 to $3,500. Length, depth, rock in the trench line and the distance to a good outlet drive the total.