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Drainage fixture unit values as given in Table 18-29-709.1 designate the relative load weight of different kinds of fixtures that shall be employed in estimating the total load carried by a soil or waste pipe, and shall be used in connection with Tables 18-29-710A and 18-29-710B of sizes for soil, waste and vent pipes for which the permissible load is given in terms of fixture units.
Fixture Type | Drainage Fixture Unit Value as Load Factors | Minimum Size of Trap (inches) |
Fixture Type | Drainage Fixture Unit Value as Load Factors | Minimum Size of Trap (inches) |
Automatic clothes washers, commercial a, g |
3 | 2 |
Automatic clothes washers, residential g |
2 | 2 |
Bathroom group as defined in Section 202 (≤ 1.6 gpf water closet) f |
5 | - |
Bathroom group as defined in Section 202 (water closet flushing greater than 1.6 gpf) f |
6 | - |
Bathtub (with or without overhead shower or whirlpool attachments) b |
2 | 1 1/2 |
Bidet | 1 | 1 1/4 |
Combination sink and tray | 2 | 1 1/2 |
Dental lavatory | 1 | 1 1/4 |
Dental unit or cuspidor | 1 | 1 1/4 |
Dishwashing machine, domestic, with independent drain c |
2 | 1 1/2 |
Drinking fountain | 1/2 | 1 1/4 |
Emergency floor drain | 0 | 2 |
Floor drains h | 2 h |
2 |
Floor sinks | Note h | 2 |
Kitchen sink, commercial, with food waste | 3 | 2 |
Kitchen sink, domestic (with or without food waste disposer, dishwasher or both) | 2 | 1 1/2 |
Laundry tray (1 or 2 compartments) | 2 | 1 1/2 |
Lavatory | 1 | 1 1/4 |
Shower (based on the total flow rate through showerheads and body sprays) Flow rate: | ||
5.7 gpm or less | 2 | 1 1/2 |
Greater than 5.7 gpm to 12.3 gpm | 3 | 2 |
Greater than 12.3 gpm to 25.8 gpm | 5 | 3 |
Greater than 25.8 gpm to 55.6 gpm | 6 | 4 |
Service sink | 2 | 1 1/2 |
Sink | 2 | 1 1/2 |
Urinal | 4 | Note d |
Urinal, 1 gallon per flush or less | 2 e |
Note d |
Wash sink (circular or multiple) each set of faucets | 2 | 1 1/2 |
Water closet, flushometer tank, public or private | 4 e |
Note d |
Water closet, private (≤ 1.6 gpf) | 3 e |
Note d |
Water closet, private (flushing greater than 1.6 gpf) | 4 e |
Note d |
Water closet, public (≤ 1.6 gpf) | 4 e |
Note d |
Water closet, public (flushing greater than 1.6 gpf) | 6 e |
Note d |
For SI: 1 inch = 25.4 mm, 1 gallon = 3.785 L, gpf = gallon per flushing cycle, gpm = gallon per minute.
a. For traps larger than 3 inches, use Table 18-29-709.2.
b. A showerhead over a bathtub or whirlpool bathtub does not increase the drainage fixture unit value.
c. See Sections 18-29-709.2 through 18-29-709.5 for methods of computing unit value of fixtures not listed in this table or for rating of devices with intermittent flows.
d. Trap size shall be consistent with the fixture outlet size.
e. For the purpose of computing loads on building drains and sewers, water closets and urinals shall not be rated at a lower drainage fixture unit unless the lower values are confirmed by testing.
f. For fixtures added to a bathroom group, add the dfu value of those additional fixtures to the bathroom group fixture count.
g. See Section 18-29-406.2 for sizing requirements for fixture drain, branch drain and drainage stack for an automatic clothes washer standpipe.
h. See Sections 18-29-709.5 and 18-29-709.5.1.
(Amend Coun. J. 10-14-21, p. 37722, Art. VII, § 8)
18-29-709.2 Fixtures not listed in Table 18-29-709.1.
Fixtures not listed in Table 18-29-709.1 shall have a drainage fixture unit load based on the outlet size of the fixture in accordance with Table 18-29-709.2. The minimum trap size for unlisted fixtures shall be the size of the drainage outlet but not less than 1 1/4 inches (32 mm).
Fixture Drain or Trap Size (inches) | Drainage Fixture Unit Value |
1 1/4 | 1 |
1 1/2 | 2 |
2 | 3 |
2 1/2 | 4 |
3 | 5 |
4 | 6 |
For SI: 1 inch = 25.4 mm.
Where discharges to a waste receptor or to a drainage system are only known in gallons per minute (liters per second) values, the drainage fixture unit values for those flows shall be computed on the basis that 1 gallon per minute (0.06 L/s) of flow is equivalent to one drainage fixture unit.
(Amend Coun. J. 10-14-21, p. 37722, Art. VII, § 9; Amend Coun. J. 12-14-22, p. 58278, Art. VI, § 16)
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