How to Diagnose and Eradicate Water Hammer in Your Home

Water hammer is a fairly common occurrence in residential properties. What a lot of homeowners don’t realise is that banging or thumping water lines in your walls is a potentially serious issue, not just a simple annoyance.

At the very least excessive water pressure will eventually lead to leaks, but double up pressure spikes with a water heater featuring a failed pressure relief valve and you’ve got an explosive situation on your hands. Literally.

Don’t brush off water hammer as one of your home’s quirky personality traits. Get it taken care of, pronto.

Before we dive into fixing water hammer, let’s make sure that this is in fact your problem.

Its common thatwater hammer is misdiagnosed when air pockets are the true culprit behind clanging pipes. Telling the difference is generally pretty simple. If the knocking or echoing begins when you open a valve or faucet then most likely you’ve got air in the lines. If the banging starts when a valve closes then you’ve got water hammer.

The most common valves that cause water hammer are attached to the supply lines for dishwashers and washing machines. Shut-off valves for these appliances close very quickly and they consume a greater than normal quantity of water. Heavy water flow brings about an increase in pressure. High pressure and quickly closing valves are a recipe for water hammer.

For air in the lines, drain your pipes completely and refill the system. Open faucets and valves to ensure even distribution of water and the elimination of air pockets. Solutions for water hammer vary depending on the severity of pressure spikes. Some techniques you can handle on your own and others require that you bring in a pro.

For all you cheap skates out there.
The lowest cost solution is not really the best, but we’ll throw it in here and let you decide whether or not to give it a go. Try closing intake valves to the dishwasher and washing machine half way. A half-closed valve won’t allow as much water through, thereby slowing the velocity of the water. Slower water means lower pressure and with less pressure a shut-off valve is less likely to cause water hammer.

There’s no danger in allowing less water through intake hoses, except that many appliances run off a timed fill meter and don’t actually measure how much water is entering the machine. So a half-closed valve might stop water hammer while at the same time preventing enough of the wet stuff through to get your clothes and dishes clean! You’ll lose the banging, but get dirty undies, and that’s no good.

Another low-cost troubleshooting tip that sometimes does the trick is to replace your intake connections with wider hoses. This technique won’t be effective for serious pressure spikes, but it’s a simple way to lower pressure immediately before the shut-off valve.

Our final DIY fix is to try installing an AA-size water hammer arrester directly at the cold water outlet. Arresters can be found at just about any plumbing supply store. Generally they come pre-packaged with everything you’ll need to hook it up to a standard washing machine, so you may need a few adapters if installing on a dishwasher.

She’s a doozy. Ring up the plumber.
Your best bet is to bite the bullet and hire a professional plumber. If your home is experiencing especially high water pressure there could be an issue with the pressure regulator where the water enters your home. Internal parts can get gummed up or corroded and a malfunctioning regulator is potentially dangerous, especially if you’re on city water.

If the problem is not at the regulator, then you’ll need to have a full-sized water hammer arrester installed. Arresters use a compressible air cushion and piston to absorb the pressure spikes that cause water hammer. When a valve closes quickly and water flow is suddenly stopped, the back pressure pushes the piston. The piston compresses the air in the cushion chamber to absorb any excess pressure.

Water hammer in your home is hardly the end of the world, but it’s not something to take lightly either. You know what they say about preventative maintenance!