Illinois Administrative Code
Title 77 - PUBLIC HEALTH
Part 890 - ILLINOIS PLUMBING CODE
Subpart M - INSPECTIONS, TESTS, MAINTENANCE AND ADMINISTRATION
Appendix A - Plumbing Materials, Equipment, Use Restrictions and Applicable Standards
Table O - Water Supply Fixture Units (WSFU) for a Supply System with Flushometer Water Closets

Universal Citation: 77 IL Admin Code § O
Current through Register Vol. 49, No. 13, March 28, 2025

WSFU

Demand (GPM)

Pipe Size (Inches)

Pressure Loss (PSI/100'

of Pipe)

Velocity (Ft./Sec.)

Meter Size (Inches)

10

27

11/4"

8.3

6.8

3/4"

12

28.6

11/4"

9.2

7.2

3/4"

14

30.2

11/4"

10

7.9

3/4"

16

31.8

11/4"

11

8.0

3/4"

20

35

11/2"

6.0

6.4

3/4"

25

38

11/2"

7.0

6.9

1"

30

41

11/2"

8.0

7.4

1"

35

43.8

11/2"

8.8

8.0

1"

40

46.5

2"

2.5

4.7

1"

45

49

2"

2.7

5.1

1"

50

51.5

2"

2.9

5.4

11/2"

60

55

2"

3.4

5.8

11/2"

70

58.5

2"

3.7

6.0

11/2"

80

62

2"

4.0

6.2

11/2"

90

64.8

2"

4.6

6.5

11/2"

100

67.5

2"

5.0

6.8

11/2"

120

72.5

2"

5.6

7.2

2"

140

77.5

2"

6.3

8.0

2"

160

82.5

21/2"

2.7

5.7

2"

180

87

21/2"

3.0

6.1

2"

200

91.5

21/2"

3.4

6.4

2"

225

97

21/2"

3.7

6.8

2"

250

101

21/2"

4.0

7.1

3"

275

106

21/2"

4.2

7.3

3"

300

110

21/2"

4.6

7.6

3"

350

119

3"

2.1

5.5

3"

400

126

3"

2.3

5.9

3"

450

138

3"

2.7

6.3

3"

500

145

3"

3.0

6.8

3"

600

160

3"

3.6

7.4

4"

750

178

4"

1.1

4.7

4"

1000

208

4"

1.5

5.6

4"

1250

240

4"

1.9

6.4

4"

1500

267

4"

2.3

7.0

4"

1750

294

4"

2.8

7.8

4"

2000

321

6"

0.4

3.7

6"

Agency Notes:

Where a unit of local government or the community public water supply does not require separate water service lines for irrigation or similar systems that are likely to impose continuous demands (e.g., lawn sprinkler or air conditioning systems), the following rule applies: estimate the continuous demand (in gallons per minute) for outlets/systems separately from the intermittent demand from the above fixtures, and add this amount to the demand of the fixtures (in gallons per minute).

Meter and meter yoke sizes shown in this table shall apply only to those jurisdictions or governmental units where local ordinances or community public water supply requirements do not prescribe specific sizes of meters or meter yokes. Where local ordinances or community public water supply requirements cover such sizing, those requirements shall be followed.

Disclaimer: These regulations may not be the most recent version. Illinois may have more current or accurate information. We make no warranties or guarantees about the accuracy, completeness, or adequacy of the information contained on this site or the information linked to on the state site. Please check official sources.
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