Dishwasher noise on fill
 

I recently installed a new dishwasher, replacing a very old unit that I was told hasn't worked in 10 years. The problem is that when it initially goes to fill with water it makes a sort of thrumming sound (very loud). If I turn on the hot water at the sink a little the sound goes away. Does the dishwasher have a pressure regulator of some sort and thats what I'm hearing? I dont know what our house pressure is, I still have to check that.

What you have is condition called "Water Hammer" it is cause when the water flow is suddenly stopped.

There are a devices called a water hammer arresters that can be installed in the water lines to stop the hammering.

Wouldn't I have had this problem at the faucets and such before the new dishwasher was installed? And where in the system would I have to install an arrester?

Thanks!

Doesn't sound like water hammer. Sounds like harmonic vibration. The flow of the water is matching the frequency that a stretch of your pipe wants to vibrate at. When you change the flow by opening the sink valve you change the water flow to a different speed that doesn't match the pipes vibration frequency.

Try putting something on the pipe that is vibrating to dampen the vibration. It may also be vibrating against the wood where it passes through a framing member.

If you have a valve on the dw supply line you might try adjusting it slightly to affect the water flow rate.

Hi grimace

The valve on the dishwasher closes faster then you turning the tap off so it still could be water hammer.

I'm gonna try closing the valve on it a little tonight and see if that works.

Thanks!

Would it be normal for the valve to open and close several times a second during the fill? Because its not just a single noise, it lasts for several minutes during the fill.

The pipe will rattle for a little while if it is water hammer.

The valve will only open and close once per fill.

Thats why I don't think it is water hammer. The noise starts as soon as I hit start and lasts the entire fill (later in the cycle also when it refills).

I tried throttling the supply valve last night and it did stop, but only when the valve was almost entirely shut.

When you installed the dishwasher did you use copper water line?

Is it vibrating against something?

Or is the noise right in the valve?

What is the make and model of your dishwasher?

Did you find out what your water pressure is?

Still sounds like harmonic vibration to me. Turn it on and figure out which stretch of pipe the sound is coming from and put something on it to dampen the vibration or change the frequency it vibrates at. If it's buzzing in a framing hole squirt a dab of caulk in the hole.

Well I fixed it but not sure what it was I did.

I removed the fill valve and flushed the supply line (3/8-copper). Took apart the valve and cleaned out the inlet screen but it was pretty clean as it was, and rinsed out the inlet and outlet sides of the valve really good. It fills quiet now.
On to the next little project! My house to-do list is like Earl Hickey's except I add more stuff than I can cross off.

Thanks all!!