The five common types of plumbing found in homes are PEX, PVC, ABS, copper, and galvanized pipes. PEX is a flexible material used for water supply lines. PVC and ABS are found in drain, waste, and vent pipes. Copper is used in water supply lines and can be found in older and newer homes. Drain lines and water supply lines in older houses may be made of galvanized pipe, but this material isn’t used as often in modern homes because it tends to rust over time. Many plumbers replace galvanized pipes with PEX when completing upgrades or repairs.