Which FU range is typical for a basin/sink?

• A. 0.5-1 FU
• B. 1-2 FU
• C. 2-3 FU
• D. 3-5 FU

Answer: (A)

The main idea here is how much water a basin typically needs, expressed as its fixture unit (FU). A basin is a low-demand fixture because it uses water briefly and not at high flow. That’s why it’s assigned a small FU value—usually in the range of 0.5 to 1 FU. In design calculations, you sum the FU values of all fixtures on a line or system to size the supply and fittings, and a basin contributes only a small share to that total.

A range of 0.5–1 FU makes sense because some basins may be at the lower end (0.5 FU) and standard basins at about 1 FU, reflecting typical usage. Higher ranges like 2–3 FU or 3–5 FU would indicate much larger or more demanding fixtures, which isn’t characteristic of a basin.