Selecting french drain pipes and fittings

 

The secret to good French drain system is keeping roots, soil, and debris out of the gravel and pipes. By wrapping the gravel in permeable landscape cloth and the piping in fabric drain pipe sleeve you minimize the soil and clay silt that can destroy water flow.

But roots are tricky things that will wiggle their way through every gap in your protection until they finally find their way into the drainage pipe. Once there they will grow and expand to collect as much water as they can. When they expand too much the roots will begin to block water flow through the French drain pipe.

Debris like leaves, twigs, nests, mulch, and even deceased animals are another cause of blocked French drain pipes. Drainage systems that are connected to the house downspouts or that include surface drains are especially prone to this problem.

So how do we deal with plugged pipes in a French drain? Well you could dig all the piping up every decade or so to clean it out (no thank you), or you could build your drainage system so that a plumbing company with a sewer snake - like Roto-Rooter - can quickly, easily, and safely clean you pipes anytime they need it. A sewer snake is a whirling blade on the end of a semi-flexible cable that pushed through the pipe to cut and chew through roots, soil, or debris that is blocking the pipe.

To do this you must have the right kind of pipe, the right kind of fittings, and above ground locations they can access.

Drain Pipe and Tile - If you want to be able to run a sewer snake through your French drain you MUST use rigid PVC drainage pipe (the modern drain tile).
  * Do not use the flexible corrugated perforated plastic pipe as it is too soft and the whirling blades will cut it to bits and destroy your system.

Pipe Fittings

There are many fittings available for 4" rigid PVC pipe. We are basically interested in tees, wyes, elbows, caps, and maybe reducers. As you select fittings keep in mind that you want to pick fittings that a whirling blade on the end of a semi-flexible cable can easily travel and turn through. Often a sewer snake can not make the turn in a close elbow or a bull nose tee. Also note that a sewer snake traveling across the top bar of a tee or wye fitting will skip right past the opening for the upright of the tee or wye, but when traveling through the upright it will always follow the curve in a sanitary tee or wye.
* See the Fittings drawings...