ABS

Acrylonitrile butadiene styrene is a thermoplastic polymer extruded into pipes and fittings for drainage, vent, and waste lines. The material is black or dark gray, rigid at normal temperatures, and joins using solvent cement rather than threads or mechanical couplings. It dominates North American drain-waste-vent (DWV) systems because it costs less than cast iron and installs faster than copper.

ABS pipe comes in nominal sizes from 1.25 inches to 4 inches outside diameter, with Schedule 40 being the standard for residential work. The walls are thicker than you might expect, typically 0.113 inches for 2-inch pipe, because the material must resist internal pressure spikes from water hammer and external loads from soil or concrete. Fittings, including elbows, tees, traps, and cleanout bodies, are molded as separate pieces and joined with the same solvent cement used for straight runs.

Where ABS works and where it doesn't

ABS performs well below ground and inside walls because it resists most household and municipal waste streams, does not corrode, and shrugs off freezing temperatures better than PVC. However, it degrades under prolonged UV exposure; outdoor vents must be protected with a sleeve or painted. The material also softens at around 180 degrees Fahrenheit, so it cannot carry hot water. Many jurisdictions prohibit ABS for water supply lines and require it only for DWV applications.

Installation speed is ABS's practical advantage. A joint sets in seconds when made with fast-setting cement, so a crew can assemble and test a system in one day. The downside is that a bad joint cannot be easily reworked, and an incomplete or contaminated cement bond will leak within days as the joint cures fully. Old ABS pipe from the 1980s sometimes becomes brittle and cracks; the early formulations had stability problems that modern compounds have largely solved.

Building codes vary by region. ABS is approved in most of North America for all DWV uses and is often the default choice in new construction. Some older codes still mandate cast iron for main stacks in certain building classes, and some jurisdictions require ABS to be sleeved or supported more frequently than PVC to meet thermal expansion tolerances. Always check local amendments before specifying or installing.