Ptrap

A P-trap is a plumbing component used to prevent sewer gases from entering buildings through drains. It consists of a curved section of pipe that holds a small amount of water, creating a seal between the interior drain system and the sanitary sewer. The shape roughly resembles the letter P when viewed from the side.

P-traps are commonly installed under sinks, lavatories, and bathtubs, and are also found on some appliance drains. Typical residential sizes are 1 1/4 inches or 1 1/2 inches in diameter. They can be made from brass, PVC, CPVC, ABS, or stainless steel and are connected to the tailpiece and waste line with slip joints. Proper installation requires venting to prevent siphoning of the water seal, and the trap should be accessible for cleaning and inspection.

Maintenance and common issues: the water seal can evaporate if a fixture is unused for long periods, allowing odors to escape. Traps can collect hair, soap scum, and debris, leading to clogs or slow draining. Leaks may occur at slip joints or fittings. Cleaning involves placing a bucket beneath, unscrewing the slip nuts, removing the trap, cleaning the interior, and reassembling with proper seals. Avoid aggressive chemical drain cleaners, which can damage the trap or pipes; if leaks persist, replace the trap or consult a plumber.

Code and variants: P-traps are the standard trap type for many indoor fixtures; some jurisdictions prohibit non-vented configurations like S-traps. Proper sizing, material, and venting are important for performance and code compliance.