The American Water Works Association recommends the following color scheme for painting hydrants to indicate their relative capacity. The capacity is to be determined by flow measurements of individual hydrants taken at a period of ordinary demand. When initial pressures are over 40 psig at the hydrant under test, the rating is to be based on 20 psig residual pressure, observed at the nearest hydrant connected to the same main and when no water is being drawn. When initial pressures are less than 40 psig, residual pressures shall be at least half of the initial. It is recommended that the hydrant barrel be painted chrome yellow, unless the water system prefers another color. The tops and caps of hydrants should be painted the colors indicated below to indicate hydrant capacity: |
CLASS |
COLOR
|
Hydrants
that on individual test usually have a flow capacity of:
|
CLASS AA |
1,500
gpm or greater
|
|
CLASS A |
1,000
gpm or greater
|
|
CLASS B |
500
to 1,000 gpm
|
|
CLASS C |
<500
gpm
|
It is recommended that private hydrants be painted a color that will distinguish them from public hydrants. |
FLOW RATE AND NUMBER OF HYDRANT OUTLETS REQUIRED TO FLUSH PIPELINES
Pipe
Diameter,
(inches) |
Flow
Required to Produce Velocity of Approx. 2.5 ft/s in Main
(gpm) |
Number
2.5 inch (65mm) Hydrant Outlets
|
4
|
100
|
1
|
6
|
200
|
1
|
8
|
400
|
1
|
10
|
600
|
1
|
12
|
900
|
2
|
16
|
1600
|
2
|