Water hammer (banging noise in pipes)


Listed under: plumbing, pipes, Subfloor, Services, framing

Cause

Water pressure is too high

Repair

  • water hammer (or pressure surge) generally occurs in a high-pressure system when the flow of water is suddenly stopped. A sudden fluctuation in flow velocity sets up shockwaves through the pipework, causing the pipe to vibrate making a hammering sound. It mostly occurs in metal pipes, although it can occur in plastic pipes. Fast-acting taps such as lever taps with ceramic disc washers, solenoid valves such as those in washing machines, spring-closing valves and pumps are often a cause of water hammer. It is related directly to the water velocity – the faster the water travels, the greater likelihood of water hammer

  • one option is to get a plumber to install a water hammer arrestor on the pipe upstream from the device (such as dishwasher or washing machine) that is causing the problem. These devices use a piston and air pressure to absorb the surge in pressure. This is not a DIY job – work on water supply pipes that supply sanitary fixtures (sinks, showers, toilets etc.) is restricted work that must be done by a registered plumber. You can find more information and search for a registered plumber here

  • another option if you suspect (or have been told) that too-high water pressure is the cause of the problem is to have a registered plumber install a 350 kPa pressure limiting valve on the water supply. Check that this is compatible with your plumbing fixtures and appliances. (Mains water pressure can be up to 900 kPa or even 1250 kPa in a few locations)

  • partially closing the toby to stop or reduce water hammer may work but it will also reduce volume of flow. This is not an ideal solution – before doing this, ask a registered plumber about the options

Cause

Pipes poorly attached to subfloor framing

Repair

  • add extra fixings to secure pipe against subfloor timbers where possible. Clip pipes with rubber insulated clips or clip over the pipe insulation. Fit grommets or cushioned packers where pipes pass through structural members

  • always let someone know when you intend to carry out work under a house

Cause

Air in pipes

Repair

  • open taps to let water flow through pipes and remove trapped air