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Knocking noise when running dishwasher

Posted by Skypathway1 (My Page) on
Wed, Nov 6, 13 at 10:51

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.

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:

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RE: Knocking noise when running dishwasher

I can help with this problem but it requires you to have tools and know how and be willing to use them. SOooo,before we start the procedure,in the past have you replaced facuets,replaced facuet washers and seats,repaired toilets and performed other light plumbing?
Do you make it habit paying so called pros to "fiddle around" without fixing anything?


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RE: Knocking noise when running dishwasher

klem1 - I'm thrilled you can help me. I'm not handy and I was planning to pay someone to fix the problem - but as you said I'm paying pros to fiddle without fixing.

I have never done any light plumbing. LOL I have extensive experience changing light bulbs and house painting. But I'm game to try if it's not too difficult and doesn't require fancy tools.


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RE: Knocking noise when running dishwasher

Tools and procedure is actualy quite simple but mistakes or unexpected breaks while working on water supply can change things , ( think water turned off to intire house while searching for a plumber ).
This is what I suspect is causing the noise. A loose washer in hot angle stop ( shut off valve where pipe exits wall beneath sink). 90% of the time this is the cause.
The single valve can control facuet and dish washer both or there can be 1 valve for each. If each has a valve,turn the one for facuet off. Start washer and when noise starts adjust the valve for washer( slowly turn off and/or on. If adjusting valve stops noise, you can leave it in that position until your brother-in-law can come fix it or turn hot water off at heater or main supply to house. Open the offending valve about mid way then unscrew the cap between valve and it's knob/handle. When the threads come free of valve turn valve to full open and the stem handle assembly will fall free. The screw holding washer will not be tight if my hunch is correct. You can install a new washer or just tighten the screw. Lub stem and cap with silicon grease,WD40 or the like. On reassembly,screw stem in about half way then thread cap on and snug it a little more than finger tight. Turn valve off and restore water supply. Have wrench ready to tighten cap and turn valve on. The valve will likly leak between cap and stem. Slowly tighten cap until leak/drip stops. You can't buy parts for the valve so don't overtighten and bust the cap. If the leak doesn't stop without overtightening,remove the stem again and take it to the local hardware so the clerk can help you with correct packing.
If adjusting the angle stop fails to quite the noise don't take it apart,post back and we will look elsewhere.


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RE: Knocking noise when running dishwasher

Additionally, there should be a valve controlling the DW water supply that have washers which can deteriorate, so, try changing the position of this valve.

The logic behind this, is that when you open the sink faucet the hammer stops. Well, you have changed the volume of flow when you opened the sink faucet.


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