Design & SizingQuestion 13 of 110
A 2 in trap arm connects a fixture trap to its vent. The code limits the fall in a trap arm to no more than one pipe diameter between the trap weir and the vent. What is the maximum allowable fall in this trap arm?
a.2 in
b.1/2 in
c.1 in
d.1-1/2 in
Explanation
The maximum fall equals one pipe diameter, and for a 2 in arm that is 2 in. If the arm falls more than one diameter, the vent opening drops below the crown weir and the trap can be self-siphoned. This limit is separate from and in addition to the maximum developed-length limit for the arm.
Law Reference: UPC §906.1Practice all 110 questions free — no signup required.
Related questions on this topic
- A 4 in building drain is run at the code minimum slope of 1/8 in per foot over a developed length of 96 ft. What is the total fall from the upstream end to the downstream end?
- A 2 in horizontal fixture drain must fall a total of 5 in over its run at the code minimum slope of 1/4 in per foot. How long is the run?
- A vent must be sized at not less than one-half the diameter of the drain it serves, and never smaller than 1-1/4 in. What is the minimum vent size for a 3 in drain?
- A natural-gas furnace is rated at 120,000 BTU/hr. Natural gas has a heating value of about 1,000 BTU per cubic foot. What gas volume flow, in cubic feet per hour (cfh), must the piping deliver?
- A house has three natural-gas appliances: a 100,000 BTU/hr furnace, a 40,000 BTU/hr water heater, and a 65,000 BTU/hr range. Using 1,000 BTU per cubic foot, what total cfh must the gas meter and main serve?
- A propane appliance is rated at 150,000 BTU/hr. Propane has a heating value of about 2,500 BTU per cubic foot. What is the required gas flow in cfh?
Last reviewed: · editorial process
PrepPass Editorial Team · Verified against Master Plumber Licensing Exam (UPC/IPC-based) · How we review