Research And Insight

Water hammer

Water hammer is a destructive force that relates to the incompressibility of water. The phenomenon often occurs when filling an empty pipe or quickly closing a valve. It often leads to pipe noise or even destruction of pipes, valves etc.

The water hammer pulse sent through the pipes is the sudden pressure build-up that occurs when water quickly changes momentum in a closed system.

Since water is almost incompressible, the energy of the moving water has nowhere to go if a valve is suddenly closed. This can result in a pressure wave which stresses the pipes, creating noise and in some cases destroying the pipes.


In tall buildings, water hammering is often an issue because of the high geodetic differences which often necessitate high pressure and high velocity in the build-up phase. In commercial building applications, noise is often a topic, and in that perspective avoiding water hammering is very important.

Valves to reduce damage

Water hammering becomes a risk when valves are quickly closed in a piping system (such as solenoid valves). Non-return valves are often used to avoid the shock reaching the pumps, thereby minimising the risk of destroying the pumps. On some solenoid valves, the closing time can be prolonged, thus reducing the effect of a water hammer.

In applications where a quick closing of the valves is needed, special shock absorbers can be applied. A diaphragm tank can also help suppress the effect of water hammering.

Slow pressure build-up

Water hammering also becomes a risk when filling empty pipe systems. The water hammer effect appears when the pipes are full, and the fluid suddenly stops its movement. To avoid this, it can be an advantage to fill the system slowly and let the pressure build up over a longer period of time. Some booster systems facilitate a pressure build up function and can be pre-programmed to minimise the risk of water hammering. 

The Grundfos soft pressure build-up function in pump controllers minimises the risk of water hammering and potential damage to the pipe system. 

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