Free Web Tool

Water Demand Fixture Units

Sum fixture units across plumbing fixtures and convert to peak demand using Hunter’s method — size service pipes.

Inputs

Add quantities of each fixture. Tool sums fixture units (FU) and computes peak demand via Hunter’s method.
FixtureFU eachQtySubtotal
Hunter's method
  • FU table per UPC/IPC; total FU summed across fixtures.
  • Peak Q from Hunter curve (approximated piecewise here).
  • Adjust by 0.7 for predominantly flush-tank, 1.4 for flush-valve dominated.

Results

Total FU
Peak Q (Hunter)
Daily demand (avg)
Required pipe (V≤2 m/s)