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Water Hammer – Causes and Fixes

by | Aug 22, 2019 | Plumbing

Water hammer is that loud thudding sound whenever the water stops entering your dishwasher or washing machine, or on turning off a tap. Apart from the noise sounding disturbing, it also indicates the presence of a major plumbing problem.

Why the thudding sound?

Ordinarily, plumbing pipes are designed to pressurise the water passing through them. Hence, they rush through the tap when you open it. Turning the tap off suddenly makes the water collide with the closed valve, hence producing a hydraulic shock. This shock can be highly imparting, causing different issues like loose fittings, broken or burst pipes, or damaged water-connected appliances.

Your pipes can be displaced from the jolt by the shockwaves emanating from water hammer, and in cases where strong pipe straps are used to hold the joists, these pipes may bang against your walls. This means more noise and higher chances of damage.

How to stop water hammer?

Installing air chambers is the best fix, except in cases where the plumbing system is very old. The air chamber is a short vertical pipe, usually installed right behind a valve but slightly higher than it. Instead of being filled with water, the air chambers contain air, which serves as a shock absorber whenever there is an abrupt stop in the flow of water.

Even at that, water hammer may occur at valves with air chambers installed. This is usually caused by the entry of water into the air chamber, thus making the air chamber ineffective at protecting the valve. To fix this, shut off your home’s main water valve and open the taps at the lowest and highest points of the structure. This will drain out all the remaining water in your plumbing system, allowing the air chambers to be refilled with air. Now reopen your main water valve and see if the affected appliance or tap no longer makes the thudding sound.

For plumbing systems without air chambers, installing them may be the best fix for a water hammer situation. Alternatively, you can install water hammer arrestors in such places. The arrestor is a sealed system. Thus the chances of water entering are slim. However, arrestors are only effective for a short time, unlike air chambers that could last for decades.

What is your water pressure?

Your home’s water pressure should not be too high; else you will continue to experience water hammer whether or not you have arrestors or air chambers in place. You can easily check your water pressure using a water pressure gauge. Once the gauge is screwed onto the hose bib, open the tap fully while closing all the other fixtures and taps in your home.

If you have a pressure range of 50 and 80 psi, your water pressure is safe. However, anything higher or lower means you need to take action.

The best action is to report to your local water utility so that they can bring in someone to regularise it for you at the water meter. Alternatively, you can contact a licensed plumber to install a water pressure regulator in your home.

Yes, the process of discovering a water hammer and fixing the issue is a relatively simple DIY exercise. However, it is not impossible that you face problems along the way, perhaps while installing pressure regulators or water hammer arrestors and other more complicated steps. In such cases, feel free to seek some professional assistance by bringing in a qualified local plumber.

While water hammer may appear as a simple issue, it is one that must be attended to immediately.

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