Introduction

That loud, irritating banging noise that emanates from your plumbing pipework is called ‘water hammer’. It’s caused either by turning a tap off quickly, or by fast-acting valves on appliances, which draw a sudden halt to the movement of water through the pipes.

If the pressure in the system is high the water has a great deal of momentum, and when bought to a sudden halt it causes the pipes to shudder and vibrate, making something of a racket in the process.

The vibration of the pipes is not only annoying, but can allow splits and cracks, particularly at joints, to develop, so it is always advisable to address the situation as soon as possible.

Before commencing work, make sure you have all the tools you need to successfully complete the job. Use the following link for a list of basic plumbing tools:

• Basic plumbing tools & materials

There are three ways to eliminate water hammer and you can use some or all of these approaches:

Firmly afix pipework

Ensure pipework is clipped, secured and supported at regular intervals using pipe clips of the appropriate size.

Washers & valves

Ensure washers and diaphragms in ball and float valves are functioning properly.

The valves that control water flow into a toilet cistern or a cold water storage tank can become worn so that they cannot withstand the water pressure in the pipework.

Fit a Torbeck valve to a toilet cistern…

…and check the ball valve in your water storage tank is working properly.

• Making repairs to a cistern or water tank

Pressure restrictor

• You may read plenty of advice to fit a pressure-reducing valve to your incoming mains water supply. We DO NOT recommend this approach as it will simply reduce water flow and won’t address the main cause of the problem.

Instead, a pressure restrictor should be added. There are two ways of doing this:

• A 30cm (12in) length of vertical pipe should be added to the existing pipework via a T-joint as close to the source of the hammer as possible.
• The other end of this pipe is capped off, and it is filled with air which acts as a shock absorber.
• Unfortunately, this air will eventually dissolve in the water such that hammer will return unless the whole system is drained periodically to allow air back in.

• Common metal compression fittings & adaptors

Further information and useful links

• Find a Plumber near you
• Find a Plumbing Merchants near you