Final answer:
The developed length of a branch vent is measured from the Fixture to its termination in a P-trap or open air. This is because a branch vent system is designed to remove sewage gas and odors from fixtures, such as sinks and toilets, and take them outside the building.
Step-by-step explanation:
The developed length of a branch vent is typically measured from the Fixture to its termination in a P-trap or open air. This is due to the fact that a branch vent system is designed to remove sewage gas and odors from your fixtures - such as sinks, tubs, and toilets - and outside of your house. The P-trap is critical here because it holds water that forms a seal preventing the backflow of gases.
For instance, in a sink, the branch vent starts at the fixture (the sink) and ends at its termination point, which is typically routed to the P-trap or open air for venting. Similarly, in a toilet, the fixture is the toilet itself and the termination point is typically the P-trap or a vent to open air.
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