Strange water hammer

[Yang]

I bought a new Electrolux washer. Now, every time when finishing filling the water, there would be a loud bang. Did some research found out this is quite normal with newer washing machine.

I installed one mini arrestor, doesn't help too much. But something strange happen randomly. My washing machine is on the second floor. The water hammer occasionally triggered the one toilet downstairs and one upstairs filling itself. They don't happen the same time and I couldn't find the pattern. It just happens randomly. Talked to one plumber I used before who said never heard about it.

Interested to see if anyone here has some ideas why this happens.
I also want to see why the mini-arrestor doesn't work in my case.
Thanks.

 

[Jadnashua]

The pressure spike could exceed the shutoff capability of the toilet valve, and it momentarily opens. To work best, the arrestor needs to be as close to the offending valve as possible. You might want to try it attached to the WM verses the supply valve up at the wall on the other end of the hose. If using warm water in the WM, you need one on both the hot and cold lines. Last, you should check the static water pressure in your house. If it's over 80psi, water hammer can become more of a problem. If you can afford the slight increase in time to fill the WM tub, you could try shutting the supply lines slightly. Less flow volume, less kinetic energy, less intense hammer.

Do the supply hoses on the WM jump when the washer shuts off?

 

[Sponsor]

 

[Terry]

You will need water hammer arrestors on both the hot and the cold.
Since your toilets are being affected, I'm guessing you haven't done the cold yet?

 

[Yang]

Actually I only did cold line so far. But yes, I attached the arrestor on the faucet end. Will buy another one this weekend and attach to the washer to see if it improves.

 

[Reach4]

Also buy a pressure gauge. Check that your water pressure is not more than 80 PSI.

 

[Yang]

Thanks reach4, I will buy one from HD this week.