An S-trap is a type of plumbing trap used in drain systems to prevent the backflow of sewer gases into a building. It is named "S-trap" due to its shape resembling the letter "S" when viewed from the side.
The S-trap consists of a curved section of pipe with a downward dip followed by an upward section. The curved dip retains a small amount of water, called a water seal, which acts as a barrier against sewer gases. This water seal prevents foul odors from entering the building while allowing wastewater to flow freely through the drain.
However, S-traps have been largely phased out and are no longer used in modern plumbing installations. They have been replaced by the P-trap, which is considered more effective and reliable. The primary reason for this change is that S-traps are prone to siphoning, which can lead to the loss of the water seal and the release of sewer gases into the building.
P-traps are designed with a U-shaped bend that retains a larger water seal and provides a more secure barrier against sewer gases. They are now the standard trap used in plumbing systems and are widely recognized as a safer and more effective solution.
If your plumbing system has an S-trap, it is advisable to have it replaced with a P-trap by a professional plumber to ensure proper functionality and prevent potential issues with sewer gas odor or siphoning.