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Plumbing in the Home/Mixet valve hot flow problem


QUESTION: Problem with mixet shower valve. Suddenly my hot water flow has drastically decreased. Cold flow is fine. Affects both shower and tub flow. I replaced the cartridge. Same result. I'm guessing the problem must be an obstruction on the hot side but hate to tear out the tile. 20 year old house without flow problems anywhere else. Pretty hard water and I have had problems with filters on faucets clogging but now I have a softener so that's not a problem...I can't imagine that would affect large volume flow to the valve anyway. Any other thoughts?

ANSWER: Hello Jason,
Yes, it does sound like something is restricting the flow at that valve. These valves have fairly small internal ports for water flow. Debris or hard water scale build up can restrict them. Clearing these ports is not really possible in most cases. Replacing the valve is the usual repair.

If you need to replace that valve, you do not need to break all the tile out.  There are over sized trim plates for just this reason.  You can make a big enough hole in the tile/wall to replace the valve.  Alternately, you could open the backside of the wall if you have access.
it's a lot easier to repair drywall or plaster than tile.

Good Luck,

---------- FOLLOW-UP ----------

QUESTION: Thanks, Dana.  Unfortunately, there is a cabinet on the other side of the wall so going through the drywall isn't an option.  The current opening in the tile is only slightly larger than the pipe so I'd have to take a few tiles out and hopefully restore them and the grout to the way they look now after I'm done.  A little more of a project than I have time to tackle on my own so I guess I'll have to shell out a little extra money to pay someone to come in.

Thanks for your response!

Probably the best choice.  I've done many  through the wall but you need an angle grinder with a diamond blade to cut the tile and then use an over size "smitty" plate to cover the bigger hole.  Still not that easy unless you are a pretty good plumber and can work in tight spaces.
Good Luck

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Dana Bostick


Pretty much any residential plumbing questions. For "item specific" details such as a specific model of fixture, I will need to research and there may not be any useful information available. Note: I live and work in Southern California. We do not, as a rule, use hot water or steam heating systems, oil fired boilers or private water wells so my knowledge in those areas is pretty limited. There are others here on AllExerts that can probably answer those questions better.


Retired, Licensed General Contractor with Plumbing license. Active Home Inspector, Litigation Consultant and Infrared Thermographer, Online Marketing specialist.

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