The Water Supply Fixture Unit - WFSU - is defined by the American Uniform Plumbing Code (UPC) and is used to calculate the demand in water supply systems.
One WFSU for a singel unit corresponds to one GPM, or
- 1 WSFU = 1 GPM
The conversion can only be used for one or a few fixtures. When many fixtures are added up the number must be compensated due to the intermittent use of fixtures. The compensation is normally taken care of in probability curves or tables available for sizing water supply lines.
When special equipment or manifolds are sized the table below can be used to indicate the flowrate. Note that minimum flow rate can never be less than the fixture with the highest demand.
The tables below can be used to estimate the demand in the water supply system when the load in WSFU is known. There are tables for systems with and without flush valves.
Demand in Water Supply System without Flush Valves
Demand in Water Supply System with Flush Valves
Building Water Supply Diagram in gal/min
Building Water Supply Diagram in l/s
Hot and cold water service systems - design properties, capacities, sizing and more.
Required cold water dwelling storage capacity - commonly used fixtures and types of buildings.
Cold water storage for occupants in common types of buildings as factories, hospitals, houses and more
Design procedures for domestic hot water service systems.
Vents in draining systems protects traps against pressure differences that could cause them to siphon or blow out .
Drainage Fixture Units (DFU) connected to building drains and sewers.
Content of hot water in some common used fixtures - basins, sinks and baths.
Recommended dimensions hot and cold water pipes.
Hot water can be circulated through a return pipe if it's instantly required at the fixtures.
Consumption of hot water per person or occupant.
Maximum Drainage Fixture Unit - DFU - loads in sanitary piping systems.
Calculating expected demand for water supply service lines.
Supply requirements for common fixtures.
WSFU is used to calculate water supply service systems.
Sizing water supply service and distribution lines based on Water Supply Fixture Units (WSFU).
Sizing of water supply pipe lines.
Required water supply to public buildings.
Free online tool for designing water supply systems in buildings.