Plumbing hot/cold water mixer - where is it?

Hi all,

I had a plumber come in to look at why my hot water starts out cold, and in general doesn't get very hot in most places in the house. He found out that the hot water pump used to bring hot water upstairs was mixing with the cold water, and put in a backflow valve to stop the mixing from occurring. This helped, but there is still a bit of cold water flowing (tested when the hot water was turned off, and only hot water turned on from a tap). He thinks our hot/cold water mixer (to stop scolding) might not be working properly. We looked in several places; e.g., under the master bathroom tub but couldn't find it. Any suggestions on where this might be in a typical house?

thanks!

Not an expert, but if you are referring to an "anti-scald" valve, that is typically in the rough in valve (what is behind the wall where your tub or shower faucet is located)

Just curious, but is your house plumbed in pex? Is it all blue and red, or is some or all of it white? I ran into a similar situation a few years ago on a friend's rental property. He had hired a plumber to re-plumb the supply lines of the whole house. Long story short, the plumber had used red and blue for most of the job, but did have some white pex also. As a result, he must have gotten mixed up, and tied one of the cold white lines into a red hot line. We had to cut 4 or 5 holes into his newly drywall ed and painted ceiling to find it, but we eventually did. Obviously, he doesn't use that plumber anymore!

We traced it by starting at the water heater, and running the hot water low at a few faucets. We then went and tried to find pipes that were not as hot as they should be. We worked backwards from that cooler pipe, opening the ceiling and looking and feeling the buried pipes. Like I said, after 4 or 5 holes, we found the screw-up.

Good luck!

some shower valves have diffrent stems depending on the way
the domestic water is heated if this problem is only
in one shower valve check with the manufacturer
I have run into this a few times good luck