Earlier today, this DIY community helped me take the first step in fixing my mixing valve (which doesn't do any mixing when turned- the water stays tepid) - thank you! Now, I'm at the next stage where I was able to pop the handle off and observe what you see in this picture:

enter image description here

I'm not sure what to do next. The brass piece does not spin, not even with gently applied pliers. Is it supposed to, or is it the piece inside that's supposed to turn? Should I remove the plastic plate and see what's behind it?

Update. Removed the plate and here's what I see: enter image description here enter image description here enter image description here

  • please pull off the chrome ring ... post well lit, in focus, high resolution pictures ... a top view and a side view of the outside of the valve assembly ... a head on view looking into the valve
    – jsotola
    Feb 6, 2023 at 4:57
  • 1
    something is amiss ... I think that is a thermostatic mixing valve ... it is possible that it does not have a problem ... maybe it only requires an adjustment
    – jsotola
    Feb 6, 2023 at 5:07
  • Which part is the chrome ring? I only see brass and plastic.
    – Wynne
    Feb 6, 2023 at 6:21
  • The grey round pieces (contaminated chrome) appear to be a cosmetic trim ring that should come off fairly easily. I am not referring to the beige oval thing. Feb 6, 2023 at 21:32
  • I think Platinum Goose's answer is still applicable. Have you tried removing the cartridge? Without the sleeve around it, you may be able to use a "standard" socket, but one that big & deep would be pricey. Hit up your local home center for a set of plumbers sockets, there's sure to be one the right size in there somewhere.
    – FreeMan
    Feb 7, 2023 at 17:45

1 Answer 1


Plastic plate shows that this is a Grohe fixture. Looks like this is your valve. Grohe Thermostatic Cartridge

If so it would unscrew. You may need a special socket to remove it if a standard socket doesn't fit.

Edit: Good pictures. The valve should unscrew with a wrench or socket and can be replaced with a new valve. If it's a thermostatic valve as @jsotola indicates then maybe someone will post on how to adjust it. Also looks like there's shut offs for the water on the valve - see hex screws on each side of the valve. If so you can close each side remove the valve and take it to a plumbing supply store to get a replacement. To check close both the hex valves and slowly unscrew the cartridge valve. It may leak initially and then stop, if it does you should be able to remove it. If it doesn't stop leaking then you need to find out where the water shut off is before removing the valve. I'm guessing this is a multi family building.

  • Thanks! Can you help me understand which part of it is supposed to turn while I'm turning the now-removed handle? And >should< I unscrew this part? Is this the part that you think needs to be replaced?
    – Wynne
    Feb 6, 2023 at 13:23
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    It appears, @Wynne, that the bottom of the part in this picture is the part that's sticking out of the wall into your shower. Therefore, you'd need a wrench that will fit over those threads at the bottom and around the flats that are just above it where the word "Grohe" is engraved. You might be able to use a standard socket from your garage tool box, but most likely, you'll need a plumbers socket because those are much thinner walled and will more likely fit into the space available. If you look up the model of your faucet, it should tell you what size socket you need.
    – FreeMan
    Feb 6, 2023 at 14:18

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