Key Difference: The p Trap and S Trap and also two different species of traps provided in plumbing. The catch are types of pipe that use water to prevent the to escape of sewer gases. The S bending trap has the form of an S, if the U bend has actually a U shape, and also the p bend is shaped favor a P.

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The p Trap and S Trap and two different types of traps offered in plumbing. The traps are species of pipes that use water to prevent the escape of sewage system gases. A typical pipe connects the drainage come the sewer, however, there is nothing stopping the sewage system gases from flowing back up the pipe, leading to bad smelling gases. In fact, this was among biggest problems when indoor plumbing started off.

To counteract this, the catch was invented. In 1775, Alexander Cummings come up v the S-bend trap. This was circumvented by the U-bent catch designed by thomas Crapper in 1880. Eventually, there come the P-bend trap, which included a 90 level fitting ~ above the outlet next of a U-bend. This ns bend came to be even more popular than the other two, primarily since it was much more efficient. They room named therefore due to the form of the bend in the pipe. For example, the S bending trap has the shape of an S, when the U bend has a U shape, and also the p bend is shaped like a P.

How the trap functions is the it the bend fills v water. As the opened is blocked by water, the gases native the drainage, or the sewage line, which space not just smelly, but can at times be fairly harmful, space blocked native flowing ago upstairs into the room. However, there space times once the trap may dry out resulting in the gases flow freely. Generally this happens as soon as the drainpipe hasn’t been supplied in a while, or is faulty. In most cases, just letting the water circulation into the drainage is enough to refill the trap. However, if the is faulty or damaged, climate it is easy sufficient to replace the piping.

Another duty of the sink traps is that they additionally tend to collection any tiny but heavy object that may accidently acquire dropped down the drain. The thing gets quit at the curve and also is not enabled to flush under unless with excessive force. The curve additionally collects hair, sand, and also other debris thus stopping them native passing right into the remainder of the plumbing, i beg your pardon may result in a blockage. Hence, this traps can often be quickly detached because that cleaning or retrieving the shed object, or might instead have an outlet which allows it to be drained.

However, ns Traps are often preferred over S traps, together S traps have the tendency to easily dry out also when they room well-vented. Because of this, they cannot effectively do their project of keeping the sewer gases at bay. In fact, in some countries, like the United says the “S” traps are no longer welcomed by the pipes codes and can also be reputed illegal.

Comparison in between P Trap and also S Trap:


P Trap

S Trap

Part of



Type of

A pipes trap

A pipes trap


Shape of P

Shape of S





Water catch for drainage

Water trap for drainage

Connected to

Most frequently sinks, but can be provided for every drainage, such together toilets, floor drains, etc.

Most typically sinks, however can be offered for all drainage, such together toilets, floor drains, etc.

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More reliable at that if fairly consistent in maintain the water trap

Less efficient as it has a tendency of drying out permitting flow the gases


More recommended

Not recommended. Banned in some places like US.

Reference: Wikipedia, W.L. Gary, OWASA, Seattle Times, Hawley, Ace PlumbingImage Courtesy:,