What is a Water Hammer

Estimated reading time: 2 minutes, 41 seconds

Stop that noise

Stop that noise

“No honey, there are not ghosts in our house rattling the pipes.” Much like the “Snow Lion,” my friend’s son was having trouble seeing in the foot hills. “No son,” he said “Snow Line.” In our case, the rattling pipes are being caused by a water hammer.

A water hammer is the thumping noise heard when pipes are rattling. It Often occurs when washing machines or dishwashers automatically permit water to flow into them through a rapidly operating electronic valve or solenoid. In some cases, a water hammer is caused by chatter from poorly secured water lines. The vibration can sound horrible and be responsible for leaking conditions. Pipes really move around, and the vibrations are not good for connections.

Water hammer

According to my reliable source, a typical water hammer is caused by turbulence in the pipes. The reverberating water can cause pressures to spike to over 200PSI, and as you can imagine, your pipes can only take so much abuse before the weakest link fails.

I am considering fixing a bothersome one that runs under my bedroom floor. I am sure it is caused by some sort of issue with a frost proof outside spigot. (possibly due to a faulty integral back flow device). Like most things, unless it is a big problem, it gets ignored until I have no choice, and in my case the thumping happens rarely and is quickly forgotten.

In the old days, according to Bob Hinkle, My Father-In-Law (and retired Master Plumber), the fix was to install a length of vertical pipe or stand pipe going nowhere with a cap usually at the offending valve, in a an effort to have trapped water take up the shock. ” We were required to install a set of  them on every fixture back in Wisconsin” They would work for a while, until the air was absorbed into the water, and then fail. They could be recharged by draining the system occasionally, There was talk of bacteria growing in them and they fell out of favor”

water hammer arrestor

Bob said, “I have yet to install one while in Idaho for residential applications. New homes are equipped with an expansion tank that does provide some relief. The only time actual water hammer arrestors are used now, is in commercial applications when specified by an architect. A typical situation is when multiple toilets or urinals are located in the same room.”

Today, there are commercially available water hammer arrestors designed for this very purpose.  They can cost from $12-$35. Although I rarely hear folks complaining about, a water hammer, I recommend you take action and either secure your pipes better, and solve the issue yourself, or have a professional plumber come to the rescue.

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