We have 3-year-old shower with a "pressure-balanced" valve that is suppose to keep us from getting scalded when someone flushes the toilet. It worked fine for a while, but now temperature control is erratic and the valve makes a "thunk" noise when you turn the control handle quickly.

I hoping that I can:

  1. Replace a cartridge or something, so I don't have to..

  2. Tear out the the builtin closet behind the valve to replace the whole thing.

You can see some pictures of the valve below. It's Moen and I think it is "posi-temp" (their pressure-balanced trademark), but I can't find this particular valve online anywhere. In particular the large flat head "screw" on the right is missing from the valves I see on Moen's website and for sale at various places (Is it maybe an extra output port, I'm not using?).

Further complicating things, the "manual" Moen provides for other PosiTemp valves is nearly useless for purposes.

So, in summary, my questions are:

  1. How do I figure out what valve this is?
  2. How do I find useful documentation about this valve?
  3. What do I need to do to fix the "thunking" sound and regain control over our water temperature?


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  • Moen Customer Support: moen.com/customer-support 1 800-289-6636 - get them on the phone, it will be more efficient. Assuming you are a normal residential customer, it should be fully under warranty.
    – Ecnerwal
    Commented Aug 7, 2023 at 20:55

3 Answers 3


You should be able to get a cartridge.

You pull the little horseshoe clip ( you can see the top tab projecting from the cylinder surface ). Once the horseshoe clip is removed the cartridge can be pulled out.

I replaced some of these cartridges maybe 10 years ago and HD was able to give them to me for free under the moen lifetime warranty.


It looks like the assembly is called "M-Pact Moentrol" and seems to be discontinued (perhaps due to the deficiencies you've noticed).

There are specifications on this page with what cartridge to use, etc.

Source: Moen


Give Moen a call. They will replace most parts free of charge. They are located in Cleveland Ohio. Great customer service. It might take up to a week to get the needed parts. FYI, most of the other faucet companies have similar warranties.

  • 1
    Hi Art, downvote is not mine. But you should tour the help. Each answer is expected to add something new and meaningful. Commented Mar 11 at 12:38

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