My family and I live in an apartment. There is very hot water coming out of the cold water taps, and the toilet. I know it's summer so I expect some. In order to get even mildly cool water we have to flush the toilet, or let the water run for at least 20 minutes. The issue is just getting worse. I've put work orders into the landlord. The plumber said that this is normal. It is not. We have lived here for 3 years almost 4. This just started a few months ago and has gotten progressively worse.

After my work out I take cold showers because my apartment does not have A/C. I let the water run to purge the hot water from the pipes. In the shower we only get luke warm water now. There is no cold water on a single hand mixer. That is even when it is supposed to be on the cold area completely. After 15 minutes in the shower the water was still luke warm, no cold water coming through. While rinsing off I was burned on my inner thighs and genital area, 1st degree. I double checked the temperature gauge. Completely in the blue area. I need help. Please. I think this plumber's experience is working against him.

If anyone in our apartment building uses the water at all we finally get a bit of somewhat cold water (approx 80-90 deg F). We shouldn't get hotter water coming through when it is on the cold. As far as I can tell the boiler is dieing but I'm not sure. What can I do to help my landlord?

  • 1
    Are you on the top floor? Do your pipes come down from the ceiling/roof? Commented Jul 21, 2017 at 4:23
  • Where is this building: at least country but preferably city too? Commented Jul 21, 2017 at 10:08
  • What's the water pressure doing when this is happening? Commented Jul 21, 2017 at 11:36
  • Bottom floor, in the middle of the city. The water pressure stays stable. It just is always hot.
    – TJ Beazley
    Commented Jul 26, 2017 at 9:42

2 Answers 2


I suggest that there is a mixing valve on the hot water output side of the boiler that is supposed to feed cold water into the hot water stream so that the temperature of the potable hot water is not too high. There is supposed to be a check valve to prevent hot water from flowing in the wrong direction into the cold water line, but it has failed and hot water is flowing into the cold water line. The check valve may be integral with the mixing valve or it may be separate but next to it. The correction will be to rebuild or replace either the thermostatic mixing valve or the check valve (if there is a separate one) or both.

See http://www.watts.com/pages/learnAbout/temperingValves.asp?catId=


I agree with the other answer about the mixing valve/lack of check valve being the most probable reason.

However, I just had a first last night (which still has me searching online today, thus landing me here at this page)

I got a call for the same reason. 27 story building. The apartments are split into 2 zones for the plumbing and those zones have several risers for each stack of apartments. We only had this issue on one riser (10 apartments vertically in middle of building). Only these 10 apartments were affected, and it was only the bathrooms.

Most smaller buildings, the cold water is typically higher pressure, but this is opposite due to gravity (boiler room is on roof). After going through all 10 apartments vigorously, we isolated it down to one apartment. The bathroom sink faucet was feeding hot water into the cold line as other tenants on that riser opened up their cold.

So while a bad mixing valve or check valve issue is the most likely culprit, there is a chance it is one little faucet in the building that is screwing up everyone.

  • 1
    Yeah, single-handle mixer faucets have been known to fail in that way before, at least apocryphally Commented Sep 14, 2019 at 14:09

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