WH T&P valve drips on electric but not gas
We have a 6 gallon DSI gas & electric WH, new in 2014. On our first trip I noticed that when on electric, but not gas, the temperature & pressure relief valve would drip. So the dealership replaced ...
Forum Discussion
Hi,
Probably should check the temperature of the hot water after it has had a little while to heat up on electric.
If it is over 165F, then the pressure relief is letting out water because it is tow warm. You also risk scalding. Does your RV have a water mixing valve on the outlet of the water heater? Some are now using super hot water and a mixing valve to lower the temp to around 120F, so you would be mixing 160F water from the heater with cold water at around 60% hot and 40% cold, to get 120F output. This means that about 10 gallons of 120F water is made with 6 gallons of 160F water and 4 gallons of water from the fresh water tank.
Yes the thermostat is something to look at.
Also is the water pump on at the same time? Perhaps the water line pressure was at 60PSI when the pump stops, and you warm 65F water to 140F. This can increase the pressure in the hot water lines (there is a check valve) and opening the hot water line can release this increased pressure, as well as stop the dripping (I hope).
I was watching a TV show, and they explained that the incoming water pressure to the house was 150 PSI from the street, and there is a pressure reduction valve, much like a RV has to have only 60 PSI in the home. There is a check valve in the water heater inlet, so it will not backflow hot water into the cold water lines. What the family reported to 'This old House' was that they filled a 5 gallon bucket each week, and had to dump it weekly. The solution was a hot water rated pressure tank, and reducing the incoming water pressure to only 50 PSI. Now when nobody is using the hot water, and the tank heats from 75F to 130F, the pressure barely goes above 60 PSI, because the water is moving into the expansion tank.
Before adjusting the pressure reduction valve, and installing the expansion tank, the water pressure measured in the hose bib at the bottom of the hot water tank would increase from 70 PSI with cold water to 150 PSI with hot water, when the pressure relief valve would start to seep out some water. So the pressure relief valve was doing it's job, reliving all water pressure over 150 PSI.
Fred.
Probably should check the temperature of the hot water after it has had a little while to heat up on electric.
If it is over 165F, then the pressure relief is letting out water because it is tow warm. You also risk scalding. Does your RV have a water mixing valve on the outlet of the water heater? Some are now using super hot water and a mixing valve to lower the temp to around 120F, so you would be mixing 160F water from the heater with cold water at around 60% hot and 40% cold, to get 120F output. This means that about 10 gallons of 120F water is made with 6 gallons of 160F water and 4 gallons of water from the fresh water tank.
Yes the thermostat is something to look at.
Also is the water pump on at the same time? Perhaps the water line pressure was at 60PSI when the pump stops, and you warm 65F water to 140F. This can increase the pressure in the hot water lines (there is a check valve) and opening the hot water line can release this increased pressure, as well as stop the dripping (I hope).
I was watching a TV show, and they explained that the incoming water pressure to the house was 150 PSI from the street, and there is a pressure reduction valve, much like a RV has to have only 60 PSI in the home. There is a check valve in the water heater inlet, so it will not backflow hot water into the cold water lines. What the family reported to 'This old House' was that they filled a 5 gallon bucket each week, and had to dump it weekly. The solution was a hot water rated pressure tank, and reducing the incoming water pressure to only 50 PSI. Now when nobody is using the hot water, and the tank heats from 75F to 130F, the pressure barely goes above 60 PSI, because the water is moving into the expansion tank.
Before adjusting the pressure reduction valve, and installing the expansion tank, the water pressure measured in the hose bib at the bottom of the hot water tank would increase from 70 PSI with cold water to 150 PSI with hot water, when the pressure relief valve would start to seep out some water. So the pressure relief valve was doing it's job, reliving all water pressure over 150 PSI.
Fred.
