Factors Affecting Maximum Flow from Dry Hydrants and Dry Hydrant Sizing and Standardization

Maximum Flow Factors

Maximum flow [A] is dependant on Maximum Usable Pressure (MUP)

Where:

1. Atmospheric pressure [B]
1. Elevation above sea level
2. Atmospheric conditions [C]
2. Static lift [D]
3. Water vapor pressure [E]
1. Water temperature
4. Losses in dry hydrant
1. Pipe and fittings [F]
1. Diameter
2. Length
3. Interior roughness
2. Strainer [G]
1. Area of openings
3. Velocity head [H]
1. Diameter of pipe
4. Loss in sudden reduction [I]
1. Ration of DL and DS
5. Loss in suction hose [J]
1. Length
2. Diameter

Maximum Usable Pressure (MUP) = AP - SL - VP - MPP

Where:

AP = atmospheric pressure in psi
SL = static life in psi
VP = vapor pressure in psi
MPP = minimum pump pressure - pressure required at the suction of the pump

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