Master Plumber (UPC/IPC)

A residential branch serves the following fixtures with these water-supply fixture unit (WSFU) values: 8 water closets (tank) at 2.5 each, 8 lavatories at 1 each, and 8 showers at 2 each. What is the total demand load on the branch?

1. A60 WSFU
2. B36 WSFU
3. C52 WSFUCorrect
4. D44 WSFU

Why: Multiply each fixture count by its WSFU value and add: (8 x 2.5) + (8 x 1) + (8 x 2) = 20 + 8 + 16 = 52 WSFU. This total is what you carry into a Hunter-curve demand chart to convert fixture units to gpm. Using the wrong per-fixture value is the usual cause of a low answer such as 44.UPC §610.0

A wet-vented bathroom group discharges 5 DFU to a wet vent section. Wet vent capacity limits are 1-1/2 in = 1 DFU, 2 in = 4 DFU, and 3 in = 6 DFU. What is the minimum wet vent size?

1. A4 in
2. B2 in
3. C1-1/2 in
4. D3 inCorrect

Why: The 5 DFU load exceeds the 4 DFU capacity of a 2 in wet vent, so the next size, 3 in (6 DFU), is required. A wet vent uses an oversized drain to also serve as a vent, but only up to the fixture-unit cap for its size. Exceeding the cap forces a larger wet vent or separate venting.UPC §908.0