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Bud, Plumber
Category: Plumbing
Satisfied Customers: 556
Experience:  22 Years Field Experience - 17 Years Business Ownership - Residential or Light Commercial
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Very strange problem. Hot water runs cold in one bathroom

Customer Question

Very strange problem. Hot water runs cold in one bathroom tub and sink, but is hot everywhere else in the house. Some additional info: (1) it worked fine about 5-6 hours earlier. (2) the hot water in that bathroom is also running slower than the rest of the house, even with the hot water faucet completely open. Again, the rest of the house is normal. (3) The cold water in that bathroom runs at a normal volume. (4) The hot water heater sits in a garage closet between that bathroom and the rest of the house. Thank you.
Submitted: 8 years ago.
Category: Plumbing
Expert:  Bud replied 8 years ago.

Hi ,

Thank you for asking your question on
I am
Bud - Your personal online "Plumbing Consultant"

You have a cross connection somewhere in the plumbing. Turn on the cold water in all the faucets that are running hot out the cold. Check the hot to the rest of the house. If it is fine, a cartridge in one of the faucets has failed.




I hope the above information helps, if it does not please let me know.




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Expert:  Bud replied 8 years ago.

I have to be away from my computer for a couple hours. When I return I will be glad to finish our Q&A to help you resolve your problem. I am sorry for any inconvenience this may cause.

Expert:  Bud replied 8 years ago.
I am back online now to resume...
Customer: replied 8 years ago.
Thank you for your reply. The problem is not that hot is running out of the cold taps. The problem is that in only one bathroom, cold is running out of the hot taps (in both the tub and the sink). But I guess it could still be the cross-connect, right? Where would the cross-connect be located? The house is built on a concrete foundation, with the plumbing in the concrete. I hope the cross-connect is not buried!!!
Expert:  Bud replied 8 years ago.

I need additional information before giving an accurate answer.

Give me a little history about the house and plumbing. How old is the house? Have you lived there since it was new? Do you have a circulator pump?


Together we can solve your problem.


Please remain online with me, if you can, until we find your solution!!!


Please note: I will work hard for you and try to provide a satisfactory answer to your question, but it may require a few exchanges before we reach that satisfactory answer. I am here to help you!!!

Customer: replied 8 years ago.

Sorry about not being here. I'm on 24hr call and had to work this evening. I'll be online for several hours tonight, but I know you may already be in bed.


The house was built in 1979. I've lived here since 1990. The hot water heater was replaced about 3 years ago and seems to be working fine. As I mentioned earlier, the hot water is perfect in the rest of the house.


I've never seen this particular problem before. The only other strange problem I've seen with this bathroom is during the winter. Four or five times I've seen the cold water run really slow, just a dribble. But running the hot water for a few minutes has cleared it up. I've always just attributed this to the cold water line freezing up a bit, the lines being buried close together, and running the hot water simply thaws it out (I've never seen the hot water side freeze up, and I can't explain why not...seems to me they would both freeze up if it got cold enough to freeze up at all). The weather here lately has been in the 70s and above.


There is no circulator pump.

Customer: replied 8 years ago.
Hello. I just figured out my problem, and I think you'll be interested because you may not have run across this before, or maybe you have. I happened to notice tonight that my A/C had been running continuously without cooling the house much since about the time the problem with the hot water in the bathroom cropped up. Then it hit me that I had seen this before about 3-4 years ago, long enough that I had "misremembered" the symptoms. In our part of the country the weather is dry most of the time, but it has been rather humid for the last couple of days. Plus the nights have been cool. This sometimes causes the A/C unit to freeze up. Anyway, I went outside and checked my A/C unit and found over an inch of ice on the main line. The condensing unit just happens to sit next to the exterior wall of our bathroom, and it's not a stretch to assume that the A/C line and the hot water line probably lie next to each other somewhere under the concrete foundation. I'm thinking when the A/C line freezes up, it in turn freezes a section of the hot water line leading to the bathroom. In fact, I noticed that what little water was coming out of the hot water tap was COLDER than the water out of the cold water tap. So I simply turned off the thermostat on the A/C, switched it to fan mode, waited about an hour to thaw out the A/C unit, and the water temperature/volume in the bathroom went back to normal. Strange but true. I'm sorry that I did not remember this before asking you about it, but I really appreciate your willingness to help. Thank you.
Expert:  Bud replied 8 years ago.
Great...I have seen this only once before where the refrigration lines were straped to some water lines and caused them to freeze...I don't think I would have ever ask the correct questions to have guided you to this tho...If you ever have another question please remember