Though household sewer and vent lines used to be made of clay, lead or cast iron, current building code regulations dictate that they be made of PVC (Polyvinyl chloride), ABS (Acrylonitrile Butadiene Styrene) and in some areas, cast iron. Sewer pipes below sinks, tubs and washing machines have P-traps, which are made of various materials.
PVC pipe is the most used pipe for sewer lines and is either white or grey. Coming in 8-foot sections, it has a diameter range of 1 1/2 to 4 inches. The pipe sections join together with PVC primer, PVC cement and PVC couplings, which come in 30, 45, 60, 90 and 180-degree (straight) angles, as well as T couplings where one pipeline joins to another.
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ABS is a hard, black plastic, with the same dimensions as PVC. No primer is needed, though ABS cement must be used. Local building code regulations dictate whether PVC or ABS sewer pipes should be used, though the two types of piping must never be joined together in one sewer line, due to different expansion rates in cold/warm weather.
Cast iron is so resilient that it has been installed in buildings since the 16th century, with some of those original pipes still in use. Where the pipe sections used to be sealed with oakum and melted lead, today a rubber gasket with steel sleeve joins cast iron pipes together. Though much heavier than conventional PVC or ABS pipe, cast iron hides the noise of water/waste traveling through the pipeline.
A P-trap connects the vertical drain pipe running down from the sink drain hole to the sewer pipe coming out of the wall. The trap has a U-shaped bend, which constantly holds water to act as a barrier for any sewer gasses traveling up the pipeline. P-traps can be PVC, ABS, chrome plated or made of rough or polished brass.