How many fixture units is a toilet?
Chloe Ramirez
Updated on April 08, 2026
How many fixture units is a toilet?
P3004. 1 DWV System Load
| TYPE OF FIXTURE OR GROUP OF FIXTURES | DRAINAGE FIXTURE UNIT VALUE (d.f.u.)a |
|---|---|
| Laundry tub | 2 |
| Shower stall | 2 |
| Water closet (1.6 gallons per flush) | 3 |
| Water closet (greater than 1.6 gallons per flush) | 4 |
What does water supply fixture unit mean?
WSFU is used to calculate water supply service systems Sponsored Links. The WSFU (Water Supply Fixture Units) is defined by the Uniform Plumbing Code (UPC) and can be used to determine water supply to fixtures and their service systems.
How are plumbing fixture units calculated?
A fixture unit is equal to one cubic foot of water drained in an 1 1/4 pipe over one minute (≈ 7.48 US gpm, ≈ 0.47 l/s). Fixture Units are used in plumbing design for both water supply (WFSU) and waste water (DFU).
How many water fixture units is a washing machine?
Including minimum fixture branch pipe sizes
| Individual fixtures | Minimum fixture outlet pipe size | Number of units |
|---|---|---|
| Bath/shower combo | 1/2 inch | 4.0 |
| Bathtub or bath/shower combination with a 3/4-inch bathtub fill valve | 3/4 inch | 10.0 |
| Clothes washer | 1/2 inch | 4.0 |
| Dishwasher, domestic | 1/2 inch | 1.5 |
How many fixtures does a 1/2 inch pipe have?
A 1/2″ water line of 40′ in length can supply 6 WSFU at 35-40 psi. In most cases, the main pipeline from the street to your home is either 3/4 or 1 inch in diameter, supply branches use 3/4-inch-diameter pipe, and pipes for individual components are 1/2 inch.
How many gallons is a fixture unit?
A fixture unit is equal to 1 cubic foot (0.028 m3) of water drained in an 11⁄4 inches (32 mm) diameter pipe over one minute. One cubic foot of water is roughly 7.48 US gallons (28.3 l; 6.23 imp gal). A Fixture Unit is used in plumbing design for both water supply and waste water.
How many fixtures can be on a 2 inch drain?
How many fixture units can a 2 inch drain handle?
| DIAMETER OF PIPE (inches) | MAXIMUM NUMBER OF DRAINAGE FIXTURE UNITS (dfu) | |
|---|---|---|
| Total for horizontal branch | Total for stack greater than three branch intervals | |
| 11/2 | 3 | 8 |
| 2 | 6 | 24 |
| 21/2 | 12 | 42 |
How do you use fixture units?
How many fixture units is a kitchen sink?
Drainage and venting fixture unit values
| Individual fixtures | Minimum size trap and trap arm b | Number of units |
|---|---|---|
| Kitchen sink, domestic, with or without food waste grinder and/or dishwasher | 1-1/2 inch a | 2.0 |
| Laundry sink, one or two compartments | 1-1/2 inch a | 2.0 |
| Lavatory (wash basin) | 1-1/4 inch | 1.0 |
| Shower stall | 2 inch | 2.0 |
What are the units of a plumbing system?
Most plumbing systems consist of what’s known as DWV, which is drain, water and vent. In order to configure your system, you must decide what type of fixtures you want to install. Each fixture has an assigned unit value for the supply and for the drain.
What does fixture unit stand for in plumbing?
In plumbing, a Fixture Unit ( FU) or Drain Fixture Unit ( DFU) is “a unit of measure, based on the rate of discharge, time of operation and frequency of use of a fixture, that expresses the hydraulic load imposed by that fixture on the sanitary plumbing installation”. A Fixture Unit is not a flow rate unit but a design factor.
How to calculate drain fixture units by plumbing code?
Use the drain fixture calculation to determine the size of your venting system with the information provided in the UPC “Vents” chapter. Calculations of this nature can be relatively easy to perform, but most times plumbing is better left to the professionals.
How are fixture units used in water supply and waste water?
Fixture Units are used in plumbing design for both water supply (WFSU) and waste water (DFU). Since the fixtures in a system are never used all at the same time, the total units (capacity) achieved by adding the numbers for all fixtures must be compensated for intermittent use if we want a realistic estimate of the total drainage load.
Most plumbing systems consist of what’s known as DWV, which is drain, water and vent. In order to configure your system, you must decide what type of fixtures you want to install. Each fixture has an assigned unit value for the supply and for the drain.
In plumbing, a Fixture Unit ( FU) or Drain Fixture Unit ( DFU) is “a unit of measure, based on the rate of discharge, time of operation and frequency of use of a fixture, that expresses the hydraulic load imposed by that fixture on the sanitary plumbing installation”. A Fixture Unit is not a flow rate unit but a design factor.
Use the drain fixture calculation to determine the size of your venting system with the information provided in the UPC “Vents” chapter. Calculations of this nature can be relatively easy to perform, but most times plumbing is better left to the professionals.
Fixture Units are used in plumbing design for both water supply (WFSU) and waste water (DFU). Since the fixtures in a system are never used all at the same time, the total units (capacity) achieved by adding the numbers for all fixtures must be compensated for intermittent use if we want a realistic estimate of the total drainage load.
