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Old 12-11-2010, 04:18 AM   #1
tony14
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Default Knocking in shower valve

The shower valve in the kids' bathroom gives a kind of double knocking sound when water is turned on or off in the house, particularly when the clothes washer or dishwasher do their on-off thing.

This happened several years ago. I tried installing an air column here, a knock arrestor there, but nothing helped until we redid that bathroom and put in new shower hardware, which cured it completely.

Now the knocking has returned, and I assume we will need to break into the wall and replace the shower valve again. The second unit was a different make and model than the first. Can anyone explain to me what went wrong with these valves, and how we might avoid it in the future? We do have hard water, if that could be a factor.



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Old 12-11-2010, 06:10 AM   #2
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Maybe a washer loosened up in the valve?



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Old 12-11-2010, 12:56 PM   #3
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What brand of shower valve did you install when you remodeled?

Here is a page on water hammer arrestors that shows several types. Oops, forgot to insert the link. Here it is:http://www.plumbingsupply.com/waterhammerarresters.html One of these is intended to be attached directly to the washing machine box, and if the washing machine is one of the main culprits, putting these on could help. It is a little more difficult, but if you don't have one on the dishwasher, you can install one there as well. But you mentioned that you tried some hammer arrestors when you originally noticed the problem. Did you put in "job made arrestors", basically vertical pieces of pipe with a cap on the top, or did you install commercially made arrestors?

Since the noise is coming from the shower valve area, it is possible that you have a loose pipe in that area that is banging against something. When you remodeled, how much of the supply piping to the valve did you expose and inspect?

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Old 12-11-2010, 04:02 PM   #4
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The most common culprit in the shower area is indeed a loose pipe as phishfood suggests, usually the line to the shower head is not secured properly. Try pushing/pulling your showerhead gently, there should be no forwards and backwards movement.

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Old 12-12-2010, 10:54 PM   #5
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I listened carefully when my wife started a load of wash and the noise does seem to be coming from the shower valve area. The shower head did not move at all.

I don't recall the brand it is. Can something indeed come loose inside the control unit, like a washer as havasu suggested, or wear, or get crudded up? If so, are there rebuild kits if it is a common type? I'm wondering if I can disassemble it and take the innerds to a hardware store, or Home Depot where I got it.

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Old 12-12-2010, 11:09 PM   #6
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Depending on the valve, it is possible for parts to work loose and cause problems. However, I would expect the problem to present itself when the shower itself is used, not when other fixtures are in use.

Yes, there are rebuild kits available for many of the more popular valve models. Sometimes it is possible to take the valve apart and fix it without replacing parts, like the Kohler that I fixed for my mother this morning. Other valves, it is pretty much a matter of replacing the cartridge, period.

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Old 12-13-2010, 03:07 AM   #7
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I've attempted to attach a snapshot of the valve. Can anyone tell the maker by looking at it?

shower_valve_002_sm.jpg  
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Old 12-13-2010, 04:09 PM   #8
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Hrm, not sure of the make but I can make some semi-educated guesses as to how it comes apart.



The black part (circled in red) should unscrew counter-clockwise. You may need to grip it with pliers or a wrench, if so use a cloth or cardboard to make sure that you do not damage the outer threads.

The white part (circled in green) is your cartridge and should pull straight out after removing the black plastic ring. Make sure the water supply to the shower is shut off before doing this. Once removed you can either post a picture of the cartridge here and we can attempt to identify it for you, or take it to your local plumbing supply and they should be able to help.

There is a buildup of something on the hot water supply pipe (circled in blue) that looks suspiciously like lime or calcium from hard water. It is hard to tell from a picture. If this IS a scale buildup it may mean you have a slight leak from where that MIP is soldered to the pipe. It is possible that it is just drywall mud or grout or something similar dropped on the pipe from finishing one of the walls.

Lastly, it appears as if your shower valve and the supply pipes are just kind of "hovering" instead of being attached to anything. This could cause the valve to shake when water enters it, which could be causing your knock. While you have everything exposed, turn the shower on with a pair of pliers and see if you notice a slight thud or shaking around the valve.

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Old 12-13-2010, 04:42 PM   #9
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Thank you very kindly for the comments and instructions! There's nothing like a picture to move things along, eh?

Another question: I am assuming this is a 'pressure balanced' unit, because its installation several years ago solved a longstanding problem of the shower running hot or cold when other faucets were used. Is the pressure balancing function inside the white cartridge, or is it another part that may have to be replaced elsewhere in the unit?

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Old 12-13-2010, 11:00 PM   #10
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I THINK that you have a Price Pfister valve. If I am correct, you will need to shut the water off, drain the pressure, unscrew the 4 Phillips screws on the metal collar, and pull the cartridge out by grabbing the white stem with pliers and pulling away from the wall.



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