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35 questions from the plumbing fundamentals practice test.
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10 questions, graded as you go, with the reason for every answer. No sign-up.
Under both the IPC and the UPC, the liquid seal of a standard fixture trap must fall within what range?
B. 2 in. to 4 in.
Both model codes call for a seal of at least 2 in. and no more than 4 in. Less than 2 in. is too easily lost to pressure changes and evaporation; a much deeper seal slows flow and collects solids.
Reference: IPC 2021, Section 1002 (trap seals); UPC 2021, Section 1005
A lavatory with a long, unvented fixture drain gurgles and is left with a partly empty trap each time the basin is drained. No other fixture is in use. What is this seal loss called?
D. Self-siphonage
When the fixture's own discharge fills the drain and pulls the seal out behind it, the loss is self-siphonage. Induced siphonage is caused by the discharge of other fixtures, which the question rules out.
Reference: IPC 2021, Chapter 9 (vents); UPC 2021, Chapter 9
A water closet on an upper floor is flushed. As the slug of water passes a branch connection lower on the stack, the trap of a sink on that branch loses part of its seal. What caused the loss?
C. Induced siphonage
Flow passing the branch connection lowers the air pressure in the branch, and the higher room pressure pushes seal water out of the trap. Because another fixture's discharge did it, it is induced siphonage, not self-siphonage.
Reference: IPC 2021, Chapter 9 (vents); UPC 2021, Chapter 9