Water Supply Fixture Units - WSFU

WSFU are used to determine water supply to fixtures and their service systems

The Water Supply Fixture Units (WSFU) are defined by the Uniform Plumbing Code (UPC), and can be used to determine the water supply to fixtures and their service systems.

Individual Fixtures Minimum Fixture Branch Pipe Size Water Supply Fixture Units
(inch) Private Installations Public Installations
Bathtub 1/2 4 4
Bathtub with 3/4" fill valve 3/4 10 10
Bidet 1/2 1  
Dishwasher, domestic 1/2 1.5 1.5
Drinking fountain 1/2 0.5 0.5
Hose Bibb 1/2 2.5 2.5
Lavatory 1/2 1 1
Bar sink 1/2 1 2
Clinic fauce sink 1/2 3  
Kitchen sink, domestic 1/2 1.5 1.5
Laundry sink 1/2 1.5 1.5
Service or mop basin 1/2 1.5 3
Washup basin 1/2 2  
Shower head 1/2 2 2
Urinal with flush tank 1/2 2 2
Wash fountain 3/4 4  
Water closet with gravity tank 1/2 2.5 2.5
Water closet with flushometer tank 1/2 2.5 2.5
Water cooler 1/2 0.5 0.5
  • 1 WSFU = 1 GPM = 3.79 liter/min

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

For supply pipe lines this is taken care of in the sizing tables.  

For manifolds or special equipments sizing, a formula or a table can be used.

Related Topics

  • Water Systems - Hot and cold water systems - design properties, capacities, sizing and more

Related Documents

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