WSFU Chart — Water Supply Fixture Units & GPM Demand
Water supply fixture unit values for every listed fixture and the tabulated Hunter's-curve conversion from WSFU to design demand in GPM. IPC and UPC values are kept separate — the two codes assign different loads and the UPC handles flushometer fixtures by a different method entirely. IPC values per Appendix E Tables E103.3(2) and E103.3(3) (2021 edition; unchanged 2012–2024 — and note the appendix must be specifically adopted); UPC values per Table 610.3 (2021 edition).
IPC — WSFU load values per fixture
| Fixture | Occupancy | Supply control | Total WSFU | Hot | Cold |
|---|---|---|---|---|---|
| Bathroom group | Private | Flush tank | 3.6 | 1.5 | 2.7 |
| Bathroom group | Private | Flushometer valve | 8.0 | 3.0 | 6.0 |
| Bathtub | Private | Faucet | 1.4 | 1.0 | 1.0 |
| Bathtub | Public | Faucet | 4.0 | 3.0 | 3.0 |
| Bidet | Private | Faucet | 2.0 | 1.5 | 1.5 |
| Combination fixture | Private | Faucet | 3.0 | 2.25 | 2.25 |
| Dishwashing machine | Private | Automatic | 1.4 | 1.4 | — |
| Drinking fountain | Offices, etc. | 3/8" valve | 0.25 | — | 0.25 |
| Kitchen sink | Private | Faucet | 1.4 | 1.0 | 1.0 |
| Kitchen sink | Hotel, restaurant | Faucet | 4.0 | 3.0 | 3.0 |
| Laundry trays (1 to 3) | Private | Faucet | 1.4 | 1.0 | 1.0 |
| Lavatory | Private | Faucet | 0.7 | 0.5 | 0.5 |
| Lavatory | Public | Faucet | 2.0 | 1.5 | 1.5 |
| Service sink | Offices, etc. | Faucet | 3.0 | 2.25 | 2.25 |
| Shower head | Public | Mixing valve | 4.0 | 3.0 | 3.0 |
| Shower head | Private | Mixing valve | 1.4 | 1.0 | 1.0 |
| Urinal | Public | 1" flushometer valve | 10.0 | — | 10.0 |
| Urinal | Public | 3/4" flushometer valve | 5.0 | — | 5.0 |
| Urinal | Public | Flush tank | 3.0 | — | 3.0 |
| Washing machine (8 lb) | Private | Automatic | 1.4 | 1.0 | 1.0 |
| Washing machine (8 lb) | Public | Automatic | 3.0 | 2.25 | 2.25 |
| Washing machine (15 lb) | Public | Automatic | 4.0 | 3.0 | 3.0 |
| Water closet | Private | Flushometer valve | 6.0 | — | 6.0 |
| Water closet | Private | Flush tank | 2.2 | — | 2.2 |
| Water closet | Public | Flushometer valve | 10.0 | — | 10.0 |
| Water closet | Public | Flush tank | 5.0 | — | 5.0 |
| Water closet | Public or private | Flushometer tank | 2.0 | — | 2.0 |
WSFU → GPM demand (Hunter's curve, tabulated)
| WSFU | Flush tanks (GPM) | Flushometer valves (GPM) |
|---|---|---|
| 1 | 3.0 | — |
| 2 | 5.0 | — |
| 3 | 6.5 | — |
| 4 | 8.0 | — |
| 5 | 9.4 | 15.0 |
| 6 | 10.7 | 17.4 |
| 7 | 11.8 | 19.8 |
| 8 | 12.8 | 22.2 |
| 9 | 13.7 | 24.6 |
| 10 | 14.6 | 27.0 |
| 11 | 15.4 | 27.8 |
| 12 | 16.0 | 28.6 |
| 13 | 16.5 | 29.4 |
| 14 | 17.0 | 30.2 |
| 15 | 17.5 | 31.0 |
| 16 | 18.0 | 31.8 |
| 17 | 18.4 | 32.6 |
| 18 | 18.8 | 33.4 |
| 19 | 19.2 | 34.2 |
| 20 | 19.6 | 35.0 |
| 25 | 21.5 | 38.0 |
| 30 | 23.3 | 42.0 |
| 35 | 24.9 | 44.0 |
| 40 | 26.3 | 46.0 |
| 45 | 27.7 | 48.0 |
| 50 | 29.1 | 50.0 |
| 60 | 32.0 | 54.0 |
| 70 | 35.0 | 58.0 |
| 80 | 38.0 | 61.2 |
| 90 | 41.0 | 64.3 |
| 100 | 43.5 | 67.5 |
| 120 | 48.0 | 73.0 |
| 140 | 52.5 | 77.0 |
| 160 | 57.0 | 81.0 |
| 180 | 61.0 | 85.5 |
| 200 | 65.0 | 90.0 |
| 225 | 70.0 | 95.5 |
| 250 | 75.0 | 101.0 |
| 275 | 80.0 | 104.5 |
| 300 | 85.0 | 108.0 |
| 400 | 105.0 | 127.0 |
| 500 | 124.0 | 143.0 |
| 750 | 170.0 | 177.0 |
| 1,000 | 208.0 | 208.0 |
| 1,250 | 239.0 | 239.0 |
| 1,500 | 269.0 | 269.0 |
| 1,750 | 297.0 | 297.0 |
| 2,000 | 325.0 | 325.0 |
| 2,500 | 380.0 | 380.0 |
| 3,000 | 433.0 | 433.0 |
| 4,000 | 525.0 | 525.0 |
| 5,000 | 593.0 | 593.0 |
UPC — WSFU and minimum fixture branch sizes
| Fixture | Min branch | Private | Public | Assembly | Notes |
|---|---|---|---|---|---|
| Bathtub or combination bath/shower (fill) | 1/2" | 4.0 | 4.0 | — | — |
| Bathtub, 3/4" fill valve | 3/4" | 10.0 | 10.0 | — | — |
| Bidet | 1/2" | 1.0 | — | — | — |
| Clothes washer | 1/2" | 4.0 | 4.0 | — | — |
| Dental unit or cuspidor | 1/2" | — | 1.0 | — | — |
| Dishwasher, domestic | 1/2" | 1.5 | 1.5 | — | — |
| Drinking fountain or water cooler | 1/2" | 0.5 | 0.5 | 0.75 | — |
| Hose bibb | 1/2" | 2.5 | 2.5 | — | — |
| Hose bibb, each additional | 1/2" | 1.0 | 1.0 | — | 8 |
| Lavatory | 1/2" | 1.0 | 1.0 | 1.0 | — |
| Lawn sprinkler, each head | — | 1.0 | 1.0 | — | 5 |
| Mobile home, each (minimum) † | — | 12.0 | — | — | — |
| Sink: Bar | 1/2" | 1.0 | 2.0 | — | — |
| Sink: Clinical, faucet | 1/2" | — | 3.0 | — | — |
| Sink: Clinical, flushometer valve (with or without faucet) | 1" | — | 8.0 | — | — |
| Sink: Kitchen, domestic (with or without dishwasher) | 1/2" | 1.5 | 1.5 | — | — |
| Sink: Laundry | 1/2" | 1.5 | 1.5 | — | — |
| Sink: Service or mop basin | 1/2" | 1.5 | 3.0 | — | — |
| Sink: Washup, each set of faucets | 1/2" | — | 2.0 | — | — |
| Shower, per head | 1/2" | 2.0 | 2.0 | — | — |
| Urinal, 1.0 gpf flushometer valve | 3/4" | see 7 | see 7 | — | 7 |
| Urinal, over 1.0 gpf flushometer valve | 3/4" | see 7 | see 7 | — | 7 |
| Urinal, flush tank | 1/2" | 2.0 | 2.0 | 3.0 | — |
| Urinal with drain-cleansing action | 1/2" | 1.0 | 1.0 | 1.0 | — |
| Wash fountain, circular spray | 3/4" | — | 4.0 | — | — |
| Water closet, 1.6 gpf gravity tank | 1/2" | 2.5 | 2.5 | 3.5 | — |
| Water closet, 1.6 gpf flushometer tank | 1/2" | 2.5 | 2.5 | 3.5 | — |
| Water closet, 1.6 gpf flushometer valve | 1" | see 7 | see 7 | — | 7 |
| Water closet, over 1.6 gpf gravity tank | 1/2" | 3.0 | 5.5 | 7.0 | — |
| Water closet, over 1.6 gpf flushometer valve | 1" | see 7 | see 7 | — | 7 |
UPC table notes
- 1The listed branch size serves the cold-water branch, or both the hot and cold branches.
- 2Unlisted fixtures size by analogy to a listed fixture of similar flow rate and frequency of use.
- 3Values are the load on the cold-water building supply; for fixtures with both hot and cold connections, the separate hot and cold loads may each be taken as three-quarters of the listed total.
- 4Branch sizes are nominal (inside-diameter) pipe sizes.
- 5Continuous-flow demands such as sprinklers are computed in GPM separately and added on top of the fixture-unit demand.
- 6The assembly column applies to assembly public use.
- 7Flushometer-valve fixtures carry no fixed WSFU — flushometer systems are sized under UPC 610.10 instead.
- 8The reduced value for additional hose bibbs applies when totaling building demand; the branch to each individual bibb still sizes at the full value.
How to use this chart
Count WSFU for every fixture on the segment you're sizing (the fixture unit calculator totals it for you), decide whether the system is predominantly flush tanks or flushometer valves, and read the demand table for the design GPM. That flow — with the available pressure and developed length — is what drives the pipe size, via the pipe sizing calculator or the code's sizing procedure.
IPC 101.2: appendix provisions apply only where the jurisdiction has specifically adopted that appendix. Confirm Appendix E is adopted before citing it as enforceable. Fixture units do not apply to constant-use loads such as hose bibbs, irrigation, or cooling equipment — assign those their actual GPM directly and add them on top of the fixture-unit demand.
IPC and UPC do not agree — and local amendments override both
The two codes rate the same fixtures differently — a public flush-tank water closet carries 5.0 WSFU under the IPC but 2.5 under the UPC — and the UPC refuses to assign fixed WSFU to flushometer-valve fixtures at all, sizing those systems under Section 610.10 instead. The values themselves are stable ground (IPC Appendix E is unchanged 2012–2024; UPC 610.3's numbers are unchanged 2015 through the 2024 cycle), but states amend: California, for instance, rewrites the mobile-home row. Confirm your enforced code, its edition, and its amendments.
Common questions
How do I convert WSFU to GPM?
Total the WSFU for every fixture on the system, then read the demand table: at 100 WSFU the design demand is 43.5 GPM if the system is predominantly flush tanks, or 67.5 GPM if predominantly flushometer valves. Between printed rungs, read up to the next rung. The two curves converge at 1,000 WSFU (208 GPM) and are identical above that.
Why are there two WSFU-to-GPM curves?
Flushometer valves draw a much larger burst of water than a filling flush tank, so at low fixture counts a flushometer-heavy building peaks far higher — 15 GPM at just 5 WSFU versus 9.4 GPM. As buildings get large the probabilistic averaging washes the difference out, which is why both halves of Hunter's curve meet at 1,000 WSFU.
What is the difference between WSFU and DFU?
WSFU rates the probable water-supply demand a fixture places on the piping feeding it; DFU rates the probable drainage load it discharges. They are different scales for different systems — a public flushometer water closet is 10 WSFU on the supply side under the IPC but 4 DFU on the drainage side — and they are never interchangeable.
Are the IPC and UPC WSFU values the same?
No. A public 1.6 gpf flush-tank water closet is 5.0 WSFU under IPC Appendix E but 2.5 under UPC Table 610.3, and the UPC assigns flushometer-valve fixtures no fixed WSFU at all — those systems size under UPC 610.10. Count and size within one code family, and note that IPC Appendix E only applies where a jurisdiction has specifically adopted the appendix.
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