Drain Stoppers, Strainers and Traps

Pipe size and trap shape before anything else

A drain part has to match the pipe it joins. Nominal sizes run from 1-1/4 and 1-1/2 inch for bathroom and kitchen sinks, through 2 inch for showers, to 3 and 4 inch for larger waste lines, and the name is not the real measurement: 4 inch PVC drain pipe is 4.5 inches across outside. A trap holds a plug of water that blocks sewer gas, so a 90 degree trap or P-trap must sit below the fixture.

Material has to agree with the existing pipe. PVC and ABS look alike but use different solvent cements, and flexible elastomeric couplings let you join either to cast iron or a different size with clamps. Where a metal part screws into plastic, check the thread type and tighten by hand plus a turn, since over-tightening cracks the plastic.

Finish, stoppers and what else is mixed into the list

Visible drain parts come in finishes such as polished chrome, polished brass and oil-rubbed bronze. The finish is only the surface; for durability look at the base material, with brass and stainless steel outlasting thin plated plastic. Stoppers and strainers fit by the opening in the sink, which you measure across the flange, so check that figure against the listing before you buy.

The list also holds threaded industrial fittings, push-in connectors and malleable iron parts that are not drain parts. Before adding one to a drain, check the product type, the thread standard and whether each end is male or female. Pressure ratings matter for supply lines and compressed air, but a gravity drain only needs the right size and a tight seal.

Questions about Drain Stoppers, Strainers and Traps

What does a P-trap do and where does it go?

It is the U-shaped bend under a sink or shower that keeps a seal of water in the pipe so sewer gas cannot rise into the room. It sits between the fixture's tailpiece and the wall drain, and the seal dries out if the fixture is unused for a long time.

Can I join PVC to cast iron or ABS?

Yes, with a flexible coupling that has clamps, or with a transition cement or fitting made for the pair. Ordinary PVC cement on ABS may not form a lasting bond. Check local plumbing rules, and choose the coupling for the exact pipe sizes on each side.

How do I size a replacement strainer or stopper?

Measure the sink opening across the inside of the flange, and note the drain type: a kitchen basket strainer, a bathroom pop-up or a shower strainer. The opening size in the listing must match, and the finish should match your faucet.