Knocking coming from wall when shower is turned on

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Rickmosby

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I have recently noticed a knocking sound coming from the wall located below the second floor shower. When that shower is turned on, this knocking sound begins and last a couple minutes after water is shut off. Knocking slower until it stops completely. Can anyone confirm what this is and how much it should cost if I look at having it professionally repaired vs DIY?
 

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Rickmosby

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Can you find the hot and cold that feed that shower or bathroom????? Put your hands on it while the shower is on to see if you feel anything
I can find the hot and cold feed to the bathroom sink but nothing directly to the shower. May be behind the walls? I noticed its only when the hot water is on and only master bedroom shower, not the guest room shower which is not too far from it.
 

TomFOhio

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A lot of times the hot water line makes the noise your hearing when it is tight going through a drilled
out hole in the wall.
 

Rickmosby

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A lot of times the hot water line makes the noise your hearing when it is tight going through a drilled
out hole in the wall.
Going to look in the crawl space this weekend. Is this something I would be able to confirm looking up from the crawl space or am I looking at needing to break through the wall? I assume it would need to be insulated and/or drill hole enlarged? Sorry. Super green first timer here.
 

Twowaxhack

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It’s probably a loose washer, bad cartridge or expansion and contraction.

I have no way to watch video posted to this forum, it doesn’t work on iPhone
 
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Rickmosby

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It’s probably a loose wall washer, bad cartridge or expansion and contraction.

I have no way to watch video posted to this forum, it doesn’t work on iPhone
I'm wondering if its a bad cartridge. If its expansion and contraction, what are my options?
 

Rickmosby

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Thank you appreciate it! Thank you all! I have the new cartridge ordered (Delta rp19804) and will be checking the crawl hopefully this weekend. Did a pressure test yesterday and it was at 68/69 psi. One last thing I noticed last night was that the hot shower in question was on but the knocking didn't occur for the first time. I checked if water heater was on but it was not. Normally when knocking happens, water heater is always on except this time. Not sure if it had enough hot water stored from previous use or if the water heater itself is a major factor. Wall with noise is about 8 to 10 feet away from wall making noise, on same floor as well.
 

Twowaxhack

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If it’s expansion then you’ll have to find where the pipe is rubbing the framing and make space.

Run just the cold water and see if it still makes the noise
 
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