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Direct answer
A horizontal drain runs 40 feet at 1/4 inch per foot. What fall is required is a TradeCert Prep study concept connected to Plumbing License Practice Test prep, not a copied official exam item. Forty feet multiplied by one-quarter inch per foot equals 10 inches of fall. Always verify licensing, certification, and testing rules with the current official candidate bulletin, state manual, code book, or testing provider before relying on a detail for compliance.
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Read the answer once, then prove it by choosing an answer in a practice question before looking at the explanation. If the miss repeats, tag the domain as Math and drill a smaller set before returning to mixed practice.
Prep path
Plumbing License Study Guide
Independent journeyman and master plumber license study guide for state-specific code review, drainage, venting, traps, water supply, fixture units, and trade math.
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Public Plumbing License Practice Test sample questions with explanations.
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