Dishwasher water hammer

[AlGreen]

Every time we do a load of dishes, the pipes rattle when the supply valve closes. I added a Sioux Chief mini rester where the supply line connects nearby under the sink, but it didn't help. I assume I need to put one right at the dishwasher valve instead, but want to confirm. Thanks.

 

[Cacher_Chick]

Your sound might be that the pipe is not fastened securely and/or at the the proper intervals, so that it can move within the wall cavity when the water is turned off. If this is the case, the arrestor will not stop it.

 

[Sponsor]

 

[Jadnashua]

To work at their best, the arrestor must be close to the offending valve (in the DW). But, that may not help if the pipes are loose..

 

[AlGreen]

I'll check the pipes. How do I judge whether they're too loose? And what are the proper intervals for fastening them?

 

[Jadnashua]

Depends somewhat on the type of pipe. squeaks, if part of it, would likely be from the pipe going through a too tight hole, but it sounds like it's more loose, so that isn't part of it. If there's an elbow that butts up against something, when the flow stops, it literally will bang into it, and likely cause some noises from the inertia, just like hitting something with a hammer. The faster the water flows, and the more it flows, the louder the hammer is.

Stopping the hammering is both an audible and a longevity issue. Movement can cause the pipe to rub against things, eventually, it can rub a hole in the pipe. It also can stress any hoses, so an arrestor is useful when you have a fast shutting valve. Most things manually controlled, don't shut off quick enough to be an issue...the flow stops gradually rather than all at once.

 

[Reach4]

Idea... suppose you firmly grasp the pipe with your hand while the dishwasher is doing its thing. It's an experiment.

Also, was there a noticeable reduction in noise with the Minirestor?