Скачать или смотреть 2019-12 - Sealing of S-trap and P-trap under the sink with strong siphon effect

Simulation of S-trap and P-trap under the sink has been carried out in OpenFOAM.

The trap under sink in our household is to use water to seal up the trap to prevent sewer gas from entering our home. In US, it appears P-trap is commonly used. In HK, bottle trap is used in household instead.

The use of S-trap has been banned in most plumbing codes in US because on rare occasions the water can be sucked out of the trap by siphon effect allowing sewer gas to enter the home. There are suggestions to change the S-trap to a P-trap by extending the trap arm to retain water in the trap. This P-trap design is slightly better, however, water can still be sucked out by siphon effect. Moreover, P-trap only design is also not allowed by most plumbing codes for new construction. Provision of proper vent for P-trap is the recommended solution.

These three simulations are created with strong siphon effect to suck water out of the trap. It is clearly seen that provision of air ventilation solves the problem and keep the P-trap sealed off by water.