Minimum cold water supply line size to a urinal?

• A. 1/2 inch
• B. 5/8 inch
• C. 3/4 inch
• D. 1 inch

Answer: (C)

The main idea is that fixtures must have a supply line large enough to deliver the required flow without a big pressure drop. Urinals, with their flush valves, need a fairly solid instantaneous flow. A 3/4 inch cold-water line provides enough cross-sectional area to meet that demand and keep friction losses from starving the valve, even if the run isn’t short or if other fixtures share the same supply.

A 1/2 inch line is usually too small to consistently meet the flush valve’s needs, leading to weak or inconsistent flushes. A 5/8 inch line isn’t a standard sizing choice and still falls short of what a typical urinal requires. A 1 inch line would work, but it’s larger than the minimum required; the question asks for the smallest adequate size, which is 3/4 inch.