Plastic pipe is used in many plumbing applications because it’s relatively inexpensive, easy to install, and impervious to corrosion. However, in some locations, plastic pipe is not allowed by code for supply piping.

Rigid pipe may be PVC (polyvinyl chloride) for cold water or drain-waste-vent (DWV) plumbing, CPVC (chlorinated polyvinyl chloride) for hot and cold water, and ABS (acrylonitrile-butadiene-styrene) for DWV piping. Flexible plastic tubing is made from PB (polybutylene) and PE (polyethylene). Plastic pipe is rated for the pressure it can handle; this rating is stamped on the outside of the pipe.

Rigid copper pipe is widely preferred for water supply piping. It's sturdy and durable, resists mineral buildup, and can handle both cold and hot water. Hard supply pipe is sold in three thicknesses: M (thin wall), L (medium wall), and K (thick wall). Most above-ground plumbing is Type M.

Both kinds of copper pipe can be joined with permanently soldered fittings or flare/compression fittings that can be disassembled.

Galvanized iron pipe and fittings were standard for water supply plumbing before 1960 and are still common. The galvanized zinc coating on the outside of this pipe resists rust and corrosion, but over time the insides of the pipes clog up with mineral deposits and eventually corrode. Watertight connections are made with threaded fittings. Larger-diameter galvanized iron pipe is used for vent plumbing in some houses.

To prevent corrosion from the electrolysis that occurs when two dissimilar metals are joined together, a dielectric union should be used anywhere copper is connected to an iron pipe.

Cast iron pipe is a strong, durable material used for DWV plumbing. Two types are common: the older “hub” or “bell-and-spigot” type joined together with lead and oakum and the newer “no-hub” or “hubless” fittings connected with special rubber gaskets and stainless-steel band clamps.