Strange water hammer

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.

 

A larger arrestor may help but I suspect you have higher than average water pressure. I'd recommend picking up a water pressure gauge to confirm the house pressure.

Water-Pressure-Test-Gauge-DP-IWTG/100175467

 

Will do. But I am puzzled why water hammer triggered toilet auto filling.

 

 

The toilet fill valve might normally shut enough to stop the normal flow of water but when the shock wave from the washing machine fill shut off happened, the toilet fill valve got pushed open a little. A moment later, the toilet float shut off the toilet filling again, this time tighter given the slightly higher level of water in the toilet tank.