Propylene Glycol in domestic hot water???

TimW

A few weeks ago the relief valve on my boiler started blowing once or twice a day. I called the plumber who has worked on it and who replaced the indirect water heater 4 years ago and he suggested I shut off the valve that allows fresh water into the system, which I did. A few days later I started getting a strong smell of propylene glycol in my domestic hot water. I called the plumber back and he suggested that the only possibility is that the water heater is bad. The smell went away after a few days (I am assuming because I lost all of the glycol out of the system) but the relief valve continues to blow with some frequency. It will not blow for a few days and then release 1/2 gallon of water in 24 hours or so. The warranty on the hot water tank is such that I have to pay for a new one and send the old one back. The manufacturer will test it and if they find it faulty they will refund the cost of the new one. The plumber is convinced that this is the only possibility at this point given the symptoms, but it is going to be a very expensive situation for me if we replace the hot water heater and the manufacturer determines there was nothing wrong with it. My questions are:
Would there be any other explanation for getting glycol into the system? And is there way to test the water heater without sending it back to be sure that this is the problem?
Thanks so much for any suggestions you can offer.

Rich_49

What is the brand and model of water heater ? Certainly sounds as if the heat exchanger ( coil ) has developed a leak . Call the manufacturer or have the plumber do so , this type of leak is often one that will not require return and testing . Most times I am given permission to just field scrap these

TimW

Thanks, Rich, it is an NTI Trin&Stor. The info I have regarding the warranty comes from the plumber's discussion with the supplier. How common is it for the coils to develop a leak? Is there anything else that could possibly be causing both the relief blow off and the glycol getting into the domestic hot water?

Jamie Hall

About the only way the glycol could have gotten into the domestic hot water is a leak where the heating water -- containing the glycol -- is in a pipe etc. with the domestic hot water on the other side. This will allow both symptoms -- the glycol gets into the dhw when the heating water pressure is high, but the normally high domestic pressure leaks lets water into the heating system -- and blows the pressure relief.

The bad news here is that while propylene glycol isn't toxic -- it's used in a surprising number of human contact products -- it's not all that desirable, either -- and once this is fixed you should completely flush the whole domestic hot water system.

EBEBRATT-Ed

when the tank is disconnected the connections can be capped and the tank can be pressurized with water or air and the leak can be confirmed

TimW

Thank you all. I contacted the folks at NTI directly and they told me that I did not need to send the tank back for testing (which is what the supplier had told the plumber) and agreed that the only way that glycol could have gotten into the domestic hot water is a leak in the tank. So I will go ahead and swap out the tank this weekend. Once the new tank is in, what do I need to do to totally flush the system and make sure the glycol is completely out of the domestic hot water?

TimW

One more question...I awoke in the middle of the night last night and the hot water baseboards in one zone of the house (the upstairs) were very hot even though the thermostat for that zone was not calling for heat (it was set to 58 and the temperature was 73). Is this related to the issue of the leak in the tank or just a very weird coincidence that needs separate diagnosing?

EBEBRATT-Ed

Probably a separate problem.
Just run the hot water a while and turn the tank temperature higher than normal for a few hours. then set it back to normal