Water too hot in condo unit

branimal · April 21

My rental condo unit's master bathroom is getting very little cold water and then no cold water at all in the mornings (6-7am). So basically hot water coming out of the fixtures even when turned cold. This happens at all 4 fixtures. 2 sinks, a shower and a bathtub. It's been happening for a month.

The condo manager is hiring a plumber to inspect (shower body, faucets). He said he will bill me back if the issue is specific to my apartment. (He has a track record of pushing building problems back onto owners.)

1. Boiler was replaced end of October 2025. We have oldish supply pipe. Copper sweat. ~50 years old.

2. We recently got some additional common charges for pressure work b/w 5th and 6th floor. My unit is on the 5th floor.

3. And charges for a leak b/w 5th and 4th floor. (Adjacent to my unit) - not sure if DWV or Copper pipe.

4. 6th floor unit above me has low hot water pressure after a recent shutdown (Early April)

5. Another 6th floor unit (adjacent to unit above me) has very little hot water during the same time my tenants have an issue.

6. There have been recent renovations in nearby apartments.

7. My bathroom's risers come up and feed the vanity sinks, then supply the toilet. And then the shower. And then a separate bathtub. It is possible the shower catridge mixing components are damaged and allowing hot water to cross over to the cold line. This only happens in the morning. I think people are using more hot water (showers) in the morning than cold water (toilet). So the pressure on the hot side has to be so much higher than the cold side to over come the cold supply pressure so as to force hot water all the way back to the vanities. We're talking about a 10'x6' bathroom. So a lot of pipe distance and hence water volume. But I guess this is possible.

8. If the hot water pressure is that high, why is one unit on the 6th floor not getting enough hot pressure. And another unit is getting too little hot water. He ends up taking cold showers.

9. My tenants turn off the water and go to the 4th floor bathroom to get ready. (It's a duplex). No problem in that bathroom.

10. Lets go back to the new boiler. ITs a boiler not a hot water tank supplying hot water. So there is a master mixing valve. It takes 180F water and mixes it with cold to achieve ~120F. There could be some failure at the mixing valve.

11. There is also a recirculation pump. Keeps hot water available so you don't have to wait for it on the higher floors. 6 story building.

My guess is when balancing the pressure on the recirculation pump, something went wrong. Too much pressure on the 5th floor and too little pressure on the 6th floor.

What do you guys think?

Mad Dog_2 · April 21

Oh boy...that's going to take some time physically on the job. That sounds like a real one-sided situation there. Mad Dog

Larry Weingarten · April 21

Hi, the first thing I'd check for is crossover… water leaking from hot to cold in this case. Create the problem and then "look" at the plumbing with an IR camera. With a little luck, it will lead you to the problem or problems.

Yours, Larry

EdTheHeaterMan · April 21

I believe that supplying water at temperatures that could cause scalding from a common water heater system may be a code violation that the building owner is responsible for addressing, without passing the cost on to you.

Does the local Department of Health or the Authority Having Jurisdiction (AHJ) know that your landlord is supplying excessively hot water to your apartment? I would recommend documenting this as soon as possible so you have clear proof of the issue.

If your landlord later attempts to charge you for the repair by claiming the problem is specific to your unit, you will have documentation. At that point, you can involve the AHJ and request a written response confirming that maintaining code compliance is the responsibility of the property owner—not the tenant.

hot_rod · April 21

a failed check valve could be allowing the recirc hot water to push into the cold side

branimal · 10:31AM

I think I figured out what's going on..... lmk if i'm off base. (I own Apt 501)

Facts first / then an opinion.

Apt 602 – when he has water temperature issues, it’s because there isn’t enough hot water to mix with the cold. This happens in the mornings. This is the inverse of the issue Apt 501 is experiencing. (Too much hot water in the mornings). Perhaps hot water is getting diverted before it reaches 602's pipes.
Apt 601 – has been experiencing significantly less hot water pressure in the kitchen since a recent water shutoff
XYZ Plumbing has recently done work to address water pressure issues on the 6th & 5th floors.
XYZ Plumbing has recently done work to repair a pipe leak from 502 to 402.
New Boiler installed (~October 2025). New boilers exert higher effective pressure on the pipes than our decommissioned boiler. I would guess the majority of our riser and branch lines are from the mid-1980s.
Apt 501 – Very limited cold water in the mornings (~615a – 715a). After a few minutes the water is unusable at the shower and two sinks. This is the exact time slot that 602 is experiencing “not enough hot water”. Because 501 operates perfectly outside of this window, the internal hardware (shower cartridges/faucets) is clearly functional.
Apt 501’s shower, vanity sink 1 and vanity sink 2 are getting hot water when turned to the cold position during morning rush hours. What are the chances that all three cartridges are damaged at the same time? And then start working outside of the stated early morning hours.
It could be a pressure balancing issue at peak load time. There is high hot and cold water demand in the morning. (Showers/Toilets). Hot water is pressurized by a recirculating pump/ variable speed pump (new boiler). Cold water relies on street pressure. So hot water pressure becomes higher than cold water pressure and pushes into the cold lines. When water demand drops (after peak morning hours), the hot water recirculation pump reduces pressure. Hot water pressure and cold water pressure get closer to equilibrium and there is no crossover from hot to cold. This would explain the phenomena we are witnessing in the morning hours.

I don't know if we have check valves under our shut off valves. I don't recall seeing one when my bathroom/kitchen was renovated.

Jamie Hall · 11:57AM

Since all this started, I gather, when the new boiler was installed — along with, I expect, a fair amount of plumbing rearranging in the boiler room — that's where I would go looking. Not in the individual units.

One thing — it is unlikely (unless something was done incorrectly — that the recirculation pump could add any pressure. At least, it shouldn't. What it can do, however, in the absence of check valves, is take hot water from one set of lines and run it into the cold water lines of another set, when there is demand on those lines and hence lower pressure on those lines. Which it shouldn't be able to do, if there are check valves where needed.

In any event — back down to the boiler room and figure out how each unit gets its hot an cold water, where each unit's recirculation lines go, and so on. Don't assume that ANYTHING was done right until it is veriried.

hot_rod · 2:20PM

Whatpressure is the water coming into the building? How many stories? At 7 storiesn then pressure at the top will be about 30 psi lower than street level.

601 could be as simple as a plugged screen in the faucet. It sounds like a cross connection somewhere in the building.

Any janitor mop sinks? They sometimes have Y hoses that cross over. But any single handle mixer is suspect, or electronic faucets with H&C always on.

This may be a time consuming troubleshoot.

pumpcontrolguy · 2:41PM

I'd definitely suggest starting with building-wide scope rather than trying to nail anything down to a specific unit off the bat. What can you tell us about the following?

How does the building handle cold domestic water? gravity tank, booster, or is city pressure sufficient? the specific scenario your building has can change how things interact, Can you verify city pressure into the building if relying on only city pressure? Old gauges are often frozen or inaccurate, swapping in a new gauge to verify is good practice.

-hot domestic is usually pressurized through the cold so usually the hot in a building will have slightly less psi than the cold. But sometimes if a building has enough issues they will add a booster pump for additional hot pressure as a band aid fix rather than correcting plumbing issues. Since your building seems to be more on the special side, do they have a separate hot water booster?

-Verify the operation of the main mixing valve, what is your cold in, hot out, and recirc return temps. Don't just look at the thermometers that might be installed. 80% of the ones I see stopped working correctly decades ago. A thermal camera is very much preferred for this over a laser thermometer.

Water too hot in condo unit

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