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Rick, Construction Supervisor
Category: Plumbing
Satisfied Customers: 22046
Experience:  Licensed Master plumber with 40+ yrs. experience.
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Shower hot water problems. Domestic hot water source Weil

Customer Question

Shower hot water problems.
Domestic hot water source Weil McClean Gas furnace.
Tenant described problem: Turn on hot water. Initially scalding for about two minutes, then cold, then wait and it warms up, but not to hot.
I went to the apartment. Filled the tub Delta faucet all the way open to hot. Using a stop watch to measure time intervals of changing temperature. Initially scalding, but I continually kept placing my hand in the flow of water back and forth, the scalding water lasted for 3 minutes, then it reduced to what I would consider hot that lasted to the twelve minute mark at 12 minutes the water could be considered warm. At fifteen minutes the water hit the drain level. I turned off the water and tested the water in the tub. It was I and the tenant agreed to be a hot tub of water. I waited about 10 minutes and I turned on the shower. Again the Delta faucet was full on to hot. Again the water was scalding. I did not adjust the water, I kept it full on. There was no appreciable change in the water temperature for 11 minutes. I asked the tenant if someone was using the kitchen sink, or the washing machine, or the bathroom sink while they use the shower. He said no. My only conclusion is that when the water comes out scalding they, naturally, adjust the faucet to cool the water. What I cannot explain is why then, when they call for more hot water it does not return for a couple of minutes. I am relieved to learn that the furnace is delivering an adequate amount of hot water, as the tenant was requesting a separate hot water heater. Do you think that this might be a result of mixing valve at the tub? It has a push button to activate the shower. Not a very expensive unit.
Submitted: 1 year ago.
Category: Plumbing
Expert:  Rick replied 1 year ago.

Welcome to Just Answer, my name is ***** ***** I will do my best to help you with your issue. If my initial response doesn’t answer your question then let me know and we can continue our conversation.

Is there a DHW coil in the boiler? Is the tub/shower valve a single handle control? do you have a tempering valve on the hot water line out of the coil?

Customer: replied 1 year ago.
the DHW coil is in the boiler. Yes, the tub/shower valve is a single handle control. Yes, the temperature can be altered at the furnace. Can you do me a favor? The email submitted to his service was incorrect. It is a long story but my computer auto corrects my e-mail with the incorrect e-mail***@******.***. I called just answer to correct it and it did not correct. Anyways my real e-mail address is***@******.***.
Customer: replied 1 year ago.
It did it again. My real email address is***@******.***
Expert:  Rick replied 1 year ago.

I don't need your email address. This interface on my end is not via email. I wasn't asking if you could adjust the temp at the boiler. I asked do you have a tempering valve at the boiler?

Customer: replied 1 year ago.
I am not sure about that.
Expert:  Rick replied 1 year ago.

Ok first, a tempering valve is required by code. It mixes some cold water with the too hot water coming out of the boiler so the user doesn't get scalded. You mentioned scalding water so that's why I asked. Landlords can be sued by a knowledgeable tenant if the hot water leads to scald burns.Based on your description of the temp action out of the tub spout I'd say the cartridge in the shower valve is the most likely culprit. Your description seem to indicate no significant drop off in temp and since the flow from the tub spout is significantly more than from the shower head this description indicates to me that the coil has no problem keeping up. It's also possible that you could have an old Delta valve which has a separate pressure balancing piston that's hanging up and causing the temp variation your tenant claims