Types of Drain Traps

Gases, insects and foul smells can't penetrate a waste line's drain trap.

P-trap

Drain traps are required by most local plumbing codes -- traps create a barrier between the sewer and the interior of a structure. Traps aren't "one size fits all" pipe fittings; there's a trap designed for every application, such as tight spots and heavily used kitchen drains. Once you understand the variety of drain traps at your disposal, you'll be able to choose the right trap for your drain.

The p-trap is the most common type of drain trap. P-traps reside beneath kitchen and bath sink fixtures. Pipe attaches to a sink's strainer and runs vertically to the top of the p-trap. The p-trap makes a half-circle bend and then runs horizontally to a connection with the main drain line. The shape of this drain trap resembles the letter "P" turned on its side with the curved portion facing down. The curved area of the trap retains water and creates a barrier between sewer and plumbing fixture. Installation of a p-trap requires substantial working space.

S-trap

The s-trap resembles the p-trap with the exception that, following its first half-circle bend, it bends another 180 degrees to continue running along a vertical axis. This design allows the s-trap to connect with a main drain line that protrudes from the floor. S-traps are found beneath sinks in both kitchens and bathrooms. Like the p-trap, the s-trap requires substantial working space for installation.

Bottle trap

Bottle traps do away with half-circle curves and employ a cylinder, actually a length of pipe, to trap water. A pipe running from a plumbing fixture connects to the bottle trap's cylinder which extends downward and beyond a horizontal pipe that branches out to connect with the main drain line. Often, the bottom of a bottle trap is removable, allowing traps to be cleared in case of blockage. Bottle traps require little space for installation.

Shallow Curve Trap

Shallow traps appear similar to p-traps with the exception that their 180-degree curve occurs over a long distance. Curving over a longer distance reduces the depth requires to achieve a 180-degree curve and, in turn, reduces the overall height of the trap. Shallow traps often occur beneath tubs, showers and other areas that lack adequate space for other types of traps.

About the Author

Based in Hawaii, Shane Grey began writing professionally in 2004. He draws on his construction experience to write instructional home and garden articles. In addition to freelance work, Grey has held a position as an in-house copywriter for an online retailer. He holds a Bachelor of Arts in theater arts from Humboldt State University.