Trap (plumbing)

In plumbing, a trap is a curved section of pipe that is designed to retain a small amount of water at all times. The primary purpose of a trap is to prevent sewer gases from escaping into living spaces while allowing wastewater to flow through the plumbing system. Traps are typically located beneath sinks, bathtubs, and toilets. The most common type is the P-trap, which has a shape resembling the letter "P.