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Knocking noise when running dishwasher

Posted by Skypathway1 (My Page) on
Wed, Nov 6, 13 at 11:23

Every time we run the dishwasher we get horrible loud knocking sounds in the water line as the dishwasher is pulling in water. When we run the kitchen faucet the noises stop. BTW I've also posted this in plumbing. I'm hoping maybe someone here has been through this and knows what the problem is. I haven't found anything researching online.

I've had two highly recommended plumbers to the house about this problem. The first one said it was my faucet tap and replaced the parts and for awhile it was slightly better. The second one claimed it was air trapped in the pipes, drained all the water out and fiddled around - that didn't help. He then suggested the it was the dishwasher but said he had no knowledge how dishwashers worked or what the problem could be.

I believe the dishwasher is about 7-8 years old and appears to be working properly - dishes come out clean within an appropriate time frame. The machine interior is clean - no build up of debris or clogged lines.

My hot water heater is also about 7-8 years old. We have plenty of hot water for showers so I'm not sure if that is the problem? No knocking when taking showers or flushing toilets.

I need to fix this problem - we can't keep running to the kitchen to run the tap when we run the dishwasher. I don't want to pay another plumber who can't fix or at least diagnose problem.

I don't want to pay for a dishwasher repair person to come unless it is the dishwasher. And if it is the dishwasher - is it a part that can be repaired or would I need to replace it? Every time I call the appliance repair person they can't fix it and I have to buy a new one - these appliances are designed now to break down and not be repairable.

Thanks in advance for any suggestions.

Follow-Up Postings:

RE: Knocking noise when running dishwasher

I think your problem is called water hammer and you should have a look at "water hammer arrestors".


RE: Knocking noise when running dishwasher

whirlpool_trainee, thanks for the suggestion. Who installs a water hammer arrestor? Is this something a plumber does?

I'm wondering about an inlet water valve in the dishwasher - could that be the problem? Does that need to be changed?

RE: Knocking noise when running dishwasher

A plumber can do it, if you're not very DIY-handy. These things also have a life-span. One in our son's house went bad after many years, and the noise alerted him to the fact that it was time to replace it. I don't know if he DIY'd or had a plumber come in. Theirs was near the hot water heater.

RE: Knocking noise when running dishwasher

The DW valve won't need to be changed as they all work the same way. Water hammer happens if the flow of water is suddenly stopped - which is what dishwasher and washing machine valves do.


RE: Knocking noise when running dishwasher

Thanks for the additional information. I appreciate the help.


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