All plumbing codes prohibit the use of which type of traps?

All plumbing codes prohibit the use of which type of traps?

• A. S traps
• B. P traps
• C. Bottle traps
• D. Drum traps

Answer: (A)

Traps are meant to hold a water barrier that blocks sewer gases, and they must be vented so that draining water doesn’t pull that barrier away. An S-shaped trap creates a siphon because its outlet drops downward and then upward without a proper vent. When the drain is used, the flowing water can pull the trap water out of the bend, destroying the seal. With the water seal gone, sewer gases can enter the building. For that reason, codes prohibit this trap configuration. A P-trap, in contrast, is designed to retain a water seal while being vented properly, which stops siphoning. Bottle and drum traps are older designs that are harder to clean and maintain and don’t meet many modern venting standards, but the key issue here is that siphoning of the trap in an S shape compromises the seal, which is why it’s prohibited.

Traps are meant to hold a water barrier that blocks sewer gases, and they must be vented so that draining water doesn’t pull that barrier away. An S-shaped trap creates a siphon because its outlet drops downward and then upward without a proper vent. When the drain is used, the flowing water can pull the trap water out of the bend, destroying the seal. With the water seal gone, sewer gases can enter the building. For that reason, codes prohibit this trap configuration. A P-trap, in contrast, is designed to retain a water seal while being vented properly, which stops siphoning. Bottle and drum traps are older designs that are harder to clean and maintain and don’t meet many modern venting standards, but the key issue here is that siphoning of the trap in an S shape compromises the seal, which is why it’s prohibited.