Which statement is true regarding the maximum distance from the branch to the fixture?

Which statement is true regarding the maximum distance from the branch to the fixture?

• A. The maximum distance is 12 inches
• B. The maximum distance is 24 inches
• C. The maximum distance is 30 inches
• D. The maximum distance is 36 inches

Answer: (C)

The distance from a fixture’s drain to the point where it ties into the branch must be kept within a limit so the fixture’s trap remains properly vented. If that run is too long, the trap arm can become too distant from the vent, increasing the risk of siphoning and losing the trap seal, and it can also complicate maintaining the correct slope. Thirty inches is the standard maximum because it ensures the fixture drain is close enough to the branch to be reliably vented and to drain effectively. Distances beyond that weaken venting and trap protection, which is why thirty inches is the true limit.

The distance from a fixture’s drain to the point where it ties into the branch must be kept within a limit so the fixture’s trap remains properly vented. If that run is too long, the trap arm can become too distant from the vent, increasing the risk of siphoning and losing the trap seal, and it can also complicate maintaining the correct slope. Thirty inches is the standard maximum because it ensures the fixture drain is close enough to the branch to be reliably vented and to drain effectively. Distances beyond that weaken venting and trap protection, which is why thirty inches is the true limit.