Water Supply Fixture Units WSFU

WSFU is used to calculate water supply service systems based on the Uniform Plumbing Code. This tool provides fixture unit values for various plumbing fixtures to determine water supply requirements.

Fixture TypeMinimum Fixture Branch Pipe Size (inch)Water Supply Fixture Units (WSFU)
Bathtub1/24
Bathtub with 3/4" fill valve3/410
Bidet1/21
Dishwasher, domestic1/21.5
Drinking fountain1/20.5
Hose bibbs1/22.5
Lavatory1/21
Bar sink1/22
Clinic faucet sink1/23
Kitchen sink, domestic1/21.5
Laundry sink1/21.5
Service or mop basin1/23
Washup basin1/22
Shower, single head1/22
Urinal, flush tank1/22
Wash fountain3/44
Water closet, gravity flush tank1/22.5
Water closet, flushometer valve12.5
Water cooler1/20.5

Conversion Reference

  • 1 WSFU = 1 GPM = 3.79 liter/min
  • 1 in = 25.4 mm

Important Notes

This conversion is only true for one or a few fixtures. Since all fixtures in a system are never used at the same time, the total units achieved by adding the numbers for all fixtures must be compensated for their intermittent use.

For supply pipe lines, this is taken care of in the sizing tables. For manifolds or special equipment sizing, a formula or table can be used to account for intermittent fixture usage.

Water Supply Fixture Units WSFU | MEPKit Engineering Tools | MEPKit