Water Hammer

Many of us have experienced banging pipes when a tap is turned off. This is usually caused by a mains pressure system which is at high pressure. Fast-acting valves causing banging.

Alternatively, the cause can be fast-acting valves on appliances such as washing machines or dishwashers. These valves suddenly stop the water that is moving along the pipes. A shock wave results, and this causes the pipes to shudder, causing the banging.

The banging gets worse if the pipes aren’t properly supported or if the valves are worn. The trouble is that the noise isn’t just irritating: it’s also a sign that damage may be occurring. So you do need to do something about it.

New Dishwasher or Washing Machine?

You may be aware that the noise only started after someone worked on your water system or plumbing. Or maybe it began after a new washing machine or dishwasher was installed. If so, these are the areas to start looking at. Be aware, however, that when one part of a plumbed system is changed to correct the water hammer, you may find it starts up in another part of the system. Dishwashers and washing machines have a water supply that is controlled by solenoid valves. These are electrically operated, and they stop the flow of water immediately, so they can cause water hammer or a “bang” sound as the valve shuts off. However, the flexible hose that is used to connect to water supply is usually resilient enough to absorb the shut-off.

Ball and Float Valves and Fixings May Be Culprits

The hammering may also be caused by ball and float valves, worn stop valves or badly fixed pipework. Pipes must be fixed securely to the surface they are on at every couple of metres. Be aware that pipes run under the floor and through woodwork where they have been boxed in. It may pay to look at these first because as they’re not seen, they may have been less carefully fixed. When you look at the pipes, make sure that the pipe clips keep the pipes securely in place, but also that the clips are the right size and don’t allow the pipes to move in their fixings.

Water Ripples from the Tank

Another cause of hammering pipes is water ripples happening inside water tanks which have a ball/float valve controlling the water level. When water flows into the tank, the valve float rocks up and down, constantly closing and opening the valve. This causes a wave system to be set up, and this echoes along the pipes, causing the hammering sound. Plastic water tanks can flex considerably, so they should have a reinforcing plate (metal) to stop them moving.

How to Avoid Water Hammer

There are several ways to avoid this if it does occur (http://uk.grundfos.com/service-support/faqs/home-owner.html).

If the ball/float valve is no longer fit for purpose, this may cause water ripples, and another cause is if a low-pressure nozzle has been fitted to a value which is connected to a high-pressure water supply. Alternatively, UPS pumps can help ensure even circulation of liquids. The Grundfos circulating pump is a high-efficiency answer to these kinds of problems, with low noise levels and the ability to adapt to different environments within the water system. Grundfos Alpha is highly innovative but user-friendly - leave it on the factory setting and it will sort out what it needs to do to operate at peak efficiency.

If the problem persists, you may want to look at an equilibrium valve. This uses the water pressure from the inlet to promote valve closure - but these valves may be difficult to source in the UK.