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Public Health - Seattle & King County

Water Supply Fixture Units (WSFU) and minimum fixture branch pipe sizes

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:

  1. 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 three-quarters (3/4) of the listed total value of the fixture.
  2. The listed minimum supply branch pipe sizes for individual fixtures are the nominal (I.D.) pipe size.
Fixture unit table determining water pipe and master size
Meter and street services, inches
|
Building supply and branches, inches
|
Maximum allowable length in feet
40
60
80
100
150
200
250
300
400
500
600
700
800
900
1000

Pressure Range -- 30 to 45 psi **
3/4
1/2**
6
5
4
3
2
1
1
1
0
0
0
0
0
0
0
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