P-traps combine a 90° elbow with a J-shaped bend that retains a small amount of water to form a seal that allows wastewater to pass through but prevents toxic sewer gases and odors from escaping back up through the drain and into a dwelling. These traps also collect debris, which helps prevent blockages and makes it easier to recover items inadvertently flushed down the drain. P-traps connect to pipes under sinks, bathtubs, and showers.

These bends are shaped to resemble the letter "J" and retain a small amount of water to form a seal, preventing toxic sewer gases and odors from escaping back up through the drain and into a dwelling while allowing wastewater to pass through. J-bends form part of a P-trap and connect to pipes under sinks, bathtubs, and showers.