Isn't water hammer when there is a banging and a sound hence the name? My LG had that-as it was beginning the cycle, it would start adding water, suddenly turn the valve off, start it again, and repeat several times. The pipes would bang and I could almost feel a vibration. Are you experiencing any of that?

Right, and I have heard and felt it in other homes, none mine. It is an awful sound. What we have seems like, at worst, a very mild case. If the stutter was stronger, however, I do think the pipes would bang. It isn’t getting worse, so I am inclined to ignore it.

@MizLizzie

With both the faucet and the washer taps sputtering, the first things I'd check would be the aereator on the faucet and the screens in the washing machine hose connections. Be sure that they aren't getting mineral or gunk build-up on them. You'll want to check both the screens on the machine's water connections as well as the screens in the hoses where they attach to the taps.

If the aerator and fill screens are clean, then I'm wondering about what you meant when you said that when you "turn on the nearby sink tap, it, too, gives a slightly sputtering stream ..." So, is that faucet sputtering anytime you open the tap or only when the washer is in use and fiiling for a wash or rinse?

If the faucet sputters whether the washing machine is in use or not, you do not have water hammer caused by the machine. That is to say, the sputtering is caused by air getting into that water line from somewhere . Adding water hammer arrestors to the washing machine taps won't fix that problem.

OTOH, it seems to me that faucet sputtering that happens only when the washing machine is running), then you might find that water hammer arrestors on the washer fill taps might mitigate the sputtering.

Thanks, jw. The tap is fine unless the washer is filling. And again, it is SO mild. Unless it is putting some sort of undue pressure on my pipes, I am happy to ignore it.

I thought water hammer was the sound of a pipe rattling at the moment when a valve is turned from completely on to completely off abruptly.

Picture 10 people walking one behind the other, close together. The first one stops and the ones behind bump into the ones in front of them. That's what incompressible water does, especially when the valve is at the end of a long, straight run. The momentum of the flowing water has nowhere to go when the valve cuts off quickly and causes a substantial pressure build up in the pipe that causes the noise.

If there's a stuttering of the flow when it's running, I think that means it's something else.

As an aside, this topic reminded me of a really complicated problem with similar symptoms that I saw solved several years ago on the PBS show, Ask This Old House. :>) For anybody interested in this for entertainment value, here's a link to the ATOH video: https://www.youtube.com/watch?v=YTilMO3w7kI

Well, just noticed something odd. Wasn't there a lead off suggestion by Mark before armjim's comments? I'm just checking back and now It isn't showing up in my browser, anymore. Can anybody else still see it?

Weird. Yeah. Steven (?) who linked the mini-arresters from ACE Hardware. Guess he deleted.

Spitting like the faucet in that video is not water hammer.

This is water hammer. It starts at 1:13.

Yes, dadoes. That is water hammer because the washer valve seems to be opening then closing a few times, and when it closes, the pipe shakes.

I forgot to mention that too much pressure is sometimes the cause too, and a pressure reducer for the supply line (which is often needed for other reasons) will help.

Unless the washer in dadoes' video is at the far end of the house from where the supply line enters and there are no other water fixtures around, other water using things with valves would cause the same problem. Except, low flow hardware (as more recently manufactured faucets and fixtures have) would be less likely to cause a water hammer because a lower water flow wouldn't have as much momentum of movement built up to dissipate when the flow stops suddenly.

LG washers of a certain era are particularly prone to cause water hammer. There was a class action suit over it.

The water valves usually open outward or against the water pressure on most machines. They don’t have the ability to close them selves they rely on the water pressure coming in to push the water valve into the closed position when released.

The valves usually have a damper or some mechanism to prevent them closing too quickly or slamming. Helps to slow down waterflow before stoppiing Very important since water doesn’t compress. And if you have high water pressure especially and suddenly stopping flow causes a shockwave to travel down the line in reverse possibly damaging the pipes. Turns out LG did not seem to have that device on a number of their popular washing machines for quite some time even up till recently.

I am told that LG makes the washers for Kenmore and Kenmore never suffered the problem, apparently they made LG add in the feature.

Water hammer issue was made worse by the way LG washer seem to have this a tendency to continue to top off the water level throughout the wash and not a just few times but dozens.

Kenmore-branded appliances are sourced from a variety of manufacturers. The first three characters, before the period, of a full Kenmore model number ... syntax of xxx.xxxxxxxxx ... is a code for the source manufacturer. There may be more than one code for the same manufacturer depending on what type of appliance. 796 is a code for LG-sourced laundry. Whirlpool also has produced some models, the original Kenmore HE3, HE4, etc. frontloaders were Whirlpool (code 110). Some could be Samsung. A frontload model years ago was from Frigidaire/Electrolux.