Which nominal size is typically used for branches serving multiple fixtures or main feeds to a bathroom suite?

• A. 15 mm
• B. 22 mm
• C. 28 mm
• D. 32 mm

Answer: (B)

When sizing a branch that serves more than one fixture or the whole bathroom suite, the goal is to maintain adequate flow without a big pressure drop as multiple outlets are used. A 22 mm diameter provides enough cross-sectional area to carry the combined demand of several fixtures, helping to keep taps from losing pressure when more than one is open.

Smaller sizes, like 15 mm, often prove too restrictive for a bathroom group because flow becomes limited when multiple outlets run at once. Larger sizes, such as 28 mm or 32 mm, are typically reserved for main feeds or longer runs where a high flow is required across the system; they’re not usually needed for a standard bathroom branch and would be unnecessary for normal layouts. So the typical choice for branches feeding multiple fixtures or a bathroom suite is 22 mm.