What is the maximum distance from the branch to a fixture?

What is the maximum distance from the branch to a fixture?

• A. 12 inches
• B. 24 inches
• C. 36 inches
• D. 30 inches

Answer: (D)

Air needs to reach the trap to keep its seal from being sucked out when water flows. The farther a fixture is from the branch (the point where the drain ties into the rest of the system), the harder it is for the vent to provide that air quickly enough. Codes set a practical limit so every fixture trap stays vented properly. For typical residential drains on standard pipe sizes, the maximum distance from the branch to the fixture is 30 inches. Staying within this distance helps prevent trap siphon, reduces gurgling, and keeps drainage functioning smoothly. If you needed to place a fixture farther away, you’d need additional venting or a different arrangement to maintain proper venting and trap protection.

Air needs to reach the trap to keep its seal from being sucked out when water flows. The farther a fixture is from the branch (the point where the drain ties into the rest of the system), the harder it is for the vent to provide that air quickly enough. Codes set a practical limit so every fixture trap stays vented properly. For typical residential drains on standard pipe sizes, the maximum distance from the branch to the fixture is 30 inches. Staying within this distance helps prevent trap siphon, reduces gurgling, and keeps drainage functioning smoothly. If you needed to place a fixture farther away, you’d need additional venting or a different arrangement to maintain proper venting and trap protection.