I keep noticing that some washing machine box valves have water hammer arrestors. I am unfamiliar with this product.

When are they necessary?

Hydraulic shock (colloquial: "water hammer"; fluid hammer) is a pressure surge or wave caused when a fluid in motion, usually a liquid but sometimes also a gas is forced to stop or change direction suddenly; a momentum change. This phenomenon commonly occurs when a valve closes suddenly at an end of a pipeline system, and a pressure wave propagates in the pipe.

With a Washing Machine that has a control device that lets water in to fill the washer, can often cause a water hammer due to the suddenness of the water valve on the washer opening and closing and mostly happens on the abrupt closing of the inlet valve on the machine - which then transfers back to the piping of the house and will cause a jolt effect which may sound like a bang or a slap.

If the cost is not prohibitive I would buy the ones with the small silver tubes on top of the shut off valves like the ones shown here: [www.amazon.com]



Edited 2 times.

I was a plumber at a Nuclear Power Plant north of San Diego, CA and
we had 42" Steam Lines that would Steam Water Hammer from time to time
and it litterally shook the heavy Steal Beam Structure and made a very
loud noise. It would scare the crap out of everyone on the structure. The
noise was deffening.

Thank you!

The house has a water pressure tank installed. Will the action of the diaphragm in the tank do the same thing as a water hammer arrestor? Or does one tend to also need an arrestor?

Lorensr (CA),


steam condensate 'flash' is NOT water hammer


please do not confuse the OP


former fitter/plumber @ Seabrook Station, NH and several other large industrial projects

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"Measure Twice & Cut Once" - Retired U.A. Local 1 & 638

the closer to the offending fixture the water hammer arrestor is, the better it will work.

Not the same,but a plant in Chicago's South suburbs had along 6" steam line in a concrete channel and the elbow turning up out of it was close to the concrete at the end. When they fired up the steam in the morning, the pipe would expand so rapidly that the elbow hammered against the concrete making a horrendous "bang". finally, after many years the elbow cracked.

....... sounds like a failed steam (condensate) trap at the 'upturn'


... failed AND ignored


HOWEVER

it was not the 'flash over' that broke the elbow but the mechanical banging against the concrete, said movement because of 'probably' failed expansion devices and/or improper pipe restraints

==============================================

"Measure Twice & Cut Once" - Retired U.A. Local 1 & 638

more than y'all wanted, or need, to know about 'steam hammer':

[invenoeng.com]

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"Measure Twice & Cut Once" - Retired U.A. Local 1 & 638