For a 3 inch pipe, the maximum distance from fixture trap to vent is?

For a 3 inch pipe, the maximum distance from fixture trap to vent is?

• A. 6 Feet
• B. 4 Feet
• C. 5 Feet
• D. 3 Feet

Answer: (C)

In drainage design, traps must be vented within a certain distance to prevent the trap seal from being siphoned when the fixture drains. The allowable trap arm length depends on the size of the drain pipe downstream of the trap—the larger the pipe, the farther you can place the vent while still preventing siphon. For a 3-inch horizontal drain, the code permits a trap-to-vent distance of five feet. This means the vent connection must be within five feet measured horizontally from the trap outlet (trap weir). If you go beyond that distance, the vent may not relieve negative pressure quickly enough, increasing the risk of losing the trap seal or experiencing poor drainage. Thus, five feet is the maximum safe distance for a 3-inch pipe.

In drainage design, traps must be vented within a certain distance to prevent the trap seal from being siphoned when the fixture drains. The allowable trap arm length depends on the size of the drain pipe downstream of the trap—the larger the pipe, the farther you can place the vent while still preventing siphon. For a 3-inch horizontal drain, the code permits a trap-to-vent distance of five feet. This means the vent connection must be within five feet measured horizontally from the trap outlet (trap weir). If you go beyond that distance, the vent may not relieve negative pressure quickly enough, increasing the risk of losing the trap seal or experiencing poor drainage. Thus, five feet is the maximum safe distance for a 3-inch pipe.