Hot water tank pressure regulator spraying hot steamy water

[dsolo]

At boat this week end. Turned on water, hot water, etc. A couple hours later found water in bilge and condensation dripping from aft bilge area. Found hot water steaming from pressure valve. Couldn't stop valve from being partial open. I assumed valve was bad. Replaced it. Turned on water heater and everything seemed good. Would like to test hot water temp. Should I be concerned about the thermostat? Do valves go bad and open for no reason? Maybe the valve seal is bad? I couldn't tell. Has anyone had pressure build if tank is cold when turning on water heater and not using hot water? Per manufacturer of tank the set point of the thermostat is 170 degrees Fahrenheit. We did not use the hot water prior to the valve releasing. The water in the tank had to be less than 60 degrees Fahrenheit when it was turned on.

Any help would be appreciated. Boat is new to me, still learning.

Dan

[waybomb]

Valves go bad but so do thermostats. I hope you replaced with the same exact relief valve or bigger.
If hot steamy was coming out, I would bet your thermostat let the temp get up over 212f - very dangerous.

[tomschauer]

Mine did the same last year. Replaced valve, high limit and thermostat.
The relief valve works opens on high temp and / or high pressure, so if the stat doesn't turn off the heat it will open.

[mjk1040]

Relief valves just go bad. Once you replaced it, turn it back on and check your hot water temp at the tap. If it extremely high. thermostat and high limit units should be replaced.

[bud37]

Guys , I have a question....would it be possible to adjust the thermostat temp lower or are these units non adjustable ?.....

[mjk1040]

Bud, I think the true marine hot water tanks are pre set temps, no adjustment.

[tomschauer]

the factory stat is non adjustable.

[Viper]

The most common reason for relief valve failure is the lack of use. They generally fail in one of two ways; either they start to leak on their own, or worse, they fail to open when pressures exceed safety levels due to heating component failure. If you open it manually by operating the lever once a month, it will last a lot longer. If you operate it one time and it doesn't completely shut off, that's your clue to replace it before you have a t-stat and limit switch failure that it's designed to deal with. The valve is a safety device that should be inspected often. If it fails to operate under the worst conditions, you could have a catastrofic result.

The only amount of pressure that should be in the hot water tank when it's cold, is your fresh water system or dockside water pressures.

[RGrew176]

Yes, they do go bad. On my last boat the pressure relief valve started to leak. It was more than a drip. I removed the valve and took it to the local hardware store. The valve in the hardware store was exactly the same as the one I removed. I was glad to find that the relief valve on my water heater was not a "marine" relief valve. Would have cost double or triple it there were such a thing.

[dsolo]

Thanks to all. Will be checking hot water temperature this weekend. I also will start relieving pressure as the water heats up.