What is the maximum distance allowed for a trap arm before it has to vent?

The maximum distance allowed for a trap arm before it must be vented is 6 feet. This parameter is established to ensure proper drainage and prevent potential issues such as siphoning, which can occur if the trap arm is too long without a vent.

When the trap arm extends beyond this distance without proper venting, negative pressure can develop within the drainage system; this can lead to the trap being emptied of water, ultimately allowing sewer gases to enter the living space. Venting serves to alleviate this negative pressure by allowing air to enter the drainage system, ensuring that the trap maintains its water seal and functions correctly.

In plumbing codes, these specific requirements are in-place to safeguard both the functionality of the plumbing and the health and safety of occupants by maintaining a proper seal against sewer gases.