How to Eliminate / Reduce Water Hammer in the piping System

Water Hammer or surge, It is big headache  to every Industry,Why and How it is happen? before that we should know What is this?

Any Liquid media /Water, which is passing into the pipe, all of sudden the flow restricts /Shut off of it by the valve across the flow, the back pressure will created due to return the media, and which acts against the media velocity and collision happen and that creats big sound arises in the pipes, it is called water hammering Effect. 

the primary cause of water hammer in process applications is the quick closing valve, whether manual or automatic.A valve closing in 1.5 sec. or less (depending upon valve size and system conditions),can cause an abrupt stoppage of flow. The pressure spike (acoustic wave) created at rapid valve closure can easily be as high as five (5) times the system working pressure.

You can observe the fomaula and implement the same

Simplified Water Hammer Formula: P = (0.070) (V) (L) / t + P1

Where P = Increase in pressure

P1 = Inlet Pressure

V = Flow velocity in ft/sec

t = Time in sec.(Valve closing time)

L = Upstream Pipe Length in feet


An example of pressure hammer when closing a solenoid valve, with a 50 ft long

upstream pipe connection:

L = 50 ft

V = 5.0 ft / sec( recommended velocity for PVC piping design)

t = 40 ms(solenoid valve closing time is approx. 40-50 ms)

P1 = 50 psi inlet pressure

therefore, P = 0.07 x 5 x 50 / 0.040 + P1

or P = 437.5 psi + P1

Total Pressure (Spike) = 437.5 + 50 = 487.5 psi

As can be seen from the above, the pressure spike is approaching 10× the original system pressure which demonstrates the potentially catastrophic effect of water Hammer in an extreme case.

Thanks to Nitto denko

Article by Sivanandan



  1. Purushothaman says:

    Useful calculations.

0 Trackbacks

Leave a Reply

Your email address will not be published. Required fields are marked *