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.
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 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.