Water supply fixture units (WSFU)

Learn how to size your domestic water piping systems by finding the proper pressure load on the hot and cold water system.

Fixture unit table determining water pipe and master size

Pressure Range -- 30 to 45 psi**
Meter and street services, inches	Building supply and branches, inches	Maximum allowable length in feet
Meter and street services, inches	Building supply and branches, inches	40	60	80	100	150	200	250	300	400	500	600	700	800	900	1000
3/4	3/4	16	16	14	12	9	6	5	5	4	4	3	2	2	2	1
3/4	1	29	25	23	21	17	15	13	12	10	8	6	6	6	6	6
1	1	36	31	27	25	20	17	15	13	12	10	8	6	6	6	6
3/4	1-1/4	36	33	31	28	24	23	21	19	17	16	13	12	12	11	11
1	1-1/4	54	47	42	38	32	28	25	23	19	17	14	12	12	11	11
1	1-1/2	85	84	79	65	56	48	43	38	32	28	26	22	21	20	20
1	2	85	85	85	85	85	85	82	80	66	61	57	52	49	46	43
Pressure Range -- 46 to 60 psi **
3/4	1/2***	7	7	6	5	4	3	2	2	1	1	1	0	0	0	0
3/4	3/4	20	20	19	17	14	11	9	8	6	5	4	4	3	3	3
3/4	1	39	39	36	33	28	23	21	19	17	14	12	10	9	8	8
1	1	39	39	39	36	30	25	23	20	18	15	12	10	9	8	8
3/4	1-1/4	39	39	39	39	39	39	34	32	27	25	22	19	19	17	16
1	1-1/4	78	78	76	67	52	44	39	36	30	27	24	20	19	17	16
1	1-1/2	85	85	85	85	85	85	80	67	55	49	41	37	34	32	30
1	2	85	85	85	85	85	85	85	85	85	85	85	85	85	83	80
Pressure Range -- over 60 psi **
3/4	1/2***	7	7	7	6	5	4	3	3	2	1	1	1	1	1	0
3/4	3/4	20	20	20	20	17	13	11	10	8	7	6	6	5	4	4
3/4	1	39	39	39	39	35	30	27	24	21	17	14	13	12	12	11
1	1	39	39	39	39	38	32	29	26	22	18	14	13	12	12	11
3/4	1-1/4	39	39	39	39	39	39	39	39	34	28	26	25	23	22	21
1	1-1/4	78	78	78	78	74	62	53	47	39	31	26	25	23	22	21
1	1-1/2	85	85	85	85	85	85	85	85	81	64	51	48	46	43	40
1	2	85	85	85	85	85	85	85	85	85	85	85	85	85	85	85

** Available static pressure after head loss.

*** Building supply, 3/4-inch nominal size.

Individual fixtures	Minimum fixture outlet pipe size	Number of units
Bar Sink	1/2 inch	1.0
Bathtub	1/2 inch	4.0
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
Hose bib	1/2 inch	2.5
Hose bib, each additional	1/2 inch	1.0
Kitchen sink, domestic	1/2 inch	1.5
Laundry sink	1/2 inch	1.5
Lavatory (wash basin)	1/2 inch	1.0
Shower (per head)	1/2 inch	2.0
Water closet, 1.6 GPF gravity tank	1/2 inch	2.5

NOTES:

The listed fixture unit values represent their total load on the cold water service. The separate cold water and hot water fixture unit value for fixtures having both cold and hot water connections may each be taken as 3/4 of the listed total value of the fixture.
The listed minimum supply branch pipe sizes for individual fixtures are the nominal (I.D.) pipe size.