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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
Blue Fire Hydrant
1,500 gpm or greater
CLASS A
Green Fire Hydrant
1,000 gpm or greater
CLASS B
Orange Fire Hydrant
500 to 1,000 gpm
CLASS C
Red Fire Hydrant
<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

 

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