- Consider a long pipe AB connected at one end to a tank containing water to a height of H from the centre of pipe. At the outer end of the pipe, a valve to regulate the flow of water is provided.
- When the valve is completely open, the water is flowing with a velocity, V in the pipe.
- If now the valve is suddenly closed, then the momentum of flowing water get disturbed due to which a wave of high pressure will be set up.
- This wave of high pressure will be transmitted along the pipe with a velocity equal to the velocity of sound wave and may create noise called as Knocking,
- Also this wave of high pressure has the effect of hammering action on the walls of the pipe, hence it is also knowns as water hammer.
Reduce the pressure of the water supply to the building by fitting a regulator.
Lower fluid velocities. To keep water hammer low, pipe-sizing charts for some applications recommend flow velocity at or below 1.5 m/s (4.9 ft/s)
Fit slowly closing valves. Toilet fill valves are available in a quiet fill type that closes quietly.
High pipeline pressure rating (expensive).
Good pipeline control (start-up and shut-down procedures).
Shorter branch pipe lengths.
Shorter lengths of straight pipe, i.e. add elbows, expansion loops. Water hammer is related to the speed of sound in the fluid, and elbows reduce the influences of pressure waves.