Thank goodness for plastic drains. ABS and PVC pipes and fittings have made the heavy work of running drains in your house easy for the average Joe or Jill. Here are some tips on working with them, and on drainage in general.
Check the code beforehand. The regulations for the Drain/Waste/Vent (DWV) system are strict, and are designed to protect your house from contamination.
Every fixture should have a trap. This is the little U-shaped pipe which you’ll find under sinks. A little water remains in them at all times and acts as a plug to stop sewer gases from entering the house. Vents — stacks which exit through your roof — allow air to be drawn into the drainage pipe so the reverse pressure doesn’t draw water out of the trap.
The actual pipe from the tripe should resemble a “P” and not an “S”.
Drainage works on a simple principle. As long as it’s flowing downhill, it’ll go. That is if there are no clogs. The angle of a straight run doesn’t have to be immense. In fact, it shouldn’t be, or you’ll run out of space between the ceiling and the floor. A quarter inch per foot is often enough.
When planning your path, remember a few things about angles. Going from horizontal to vertical, you can have a 90-degree bend. But going from vertical to horizontal, you should have a more gradual angle. Two 45-degree fittings separated by a length of pipe allows the water to flow more smoothly.
More next time.