How to Have a P-Trap for a Shower

Access the drain pipe area under the shower and ensure that there is adequate clearance for the P-trap. In some cases, you might have to crawl underneath the home or work from the basement or floor beneath; the tub plumbing is nestled into the floor joists above. Sometimes the plumbing is encased in the concrete slab, in which case you must remove either the shower or the dirt and concrete.

Turn off the water supply to your home. Generally this is at either the water meter or the main water source. Rotate the knob or valve counterclockwise and check a faucet to ensure that the water is off.

Eliminate water and air pressure in the entire plumbing system by opening a sink faucet. Turn the shower faucet on as well to vent any localized pressure.

Remove the existing P-trap, if applicable, by unscrewing the connections between the trap and the outside drain line, and between the tub and the trap. These are large metal or PVC plastic rings. Pull the assembly out carefully (it will have dirty water in it) and discard it.

Assemble the new P-trap. There are two styles of traps -- rigid or swing-type. Each works the same, screwing together with couplings, but a swing-type allows movement. A rigid style is adequate underneath the tub, where you will never need to adjust the trap. Spread PVC adhesive around the coupling edges as you build the trap if you're using a rigid PVC trap.

Screw the coupling on one end of the P-trap to the drain tailpiece emerging from the shower. Attach the opposite end's coupling to the outgoing sewer line. Use PVC pipe glue if you're using the rigid style of trap. Insert adapters between the trap and the existing pipes if you're transitioning from PVC to metal.

Restore water flow to the shower. Run water to check for leakage and to prime the trap for work. A dry trap doesn't work, so priming may occasionally be necessary for seldom-used fixtures. Adjust the trap as needed before re-covering it with dirt, concrete, ceiling covering or flooring.