hot water tank overheating

DeniseO30 · May 5, 2012

Actually you would use an anti scald mixing valve the same as used in land based plumbing. the water in the tank should be ok even at engine temps of 160 or more.

or the NPT type.

kloudie1 · May 5, 2012

Denise is right on.. Most marine water heater manufacturers make a valve that fits on their tanks .. the ports match the tank port spacing.. either will work .. Mixes cold in at the tank hot outlet to prevent scalding..

Maine Sail · May 6, 2012

gettinthere said:
After a long run with the engine, the hot water tank, which is heated b the engine, is scalding hot. Is there a recommended way to control the temp?
One way would be a pair of valves diverting the flow away from the tank, a bypass loop. Of course, I'd forget to reloop it and have no hot water!

Please email or call the ABYC to let them know how you feel about this. I have been fighting for a change to the standards for over three years. Soon some toddler is going to get third burned and then maybe they'll wake up. It is completely unacceptable that ANY water heater can approach 200F...

As others have said you just install a thermostatic mixing valve...

Some manufacturers DO care about safety whiles others could care less. This is the mixing valve as it comes stock on an Isotemp water heater.

Maine Sail · May 6, 2012

gettinthere said:
Having near boiling conditions is OK within the system? I can smell steam when I open the hot water spigot.

Secondary issue, it's "pushing" hot water into the cold water system. I have a check valve on the feed side of the tank. I'm surprised I'd get that much heating of the water into the cold water side of my faucets.

You're engine may be running too hot. If your T&P valve is not blowing you're below that . Also an expansion tank in the pressure side of the system can help with the expansion..

Again this is currently an UNSAFE but "acceptable" installation by ABYC standards, it should NOT be "allowed" to continue.........

PLEASE email your concerns to the ABYC. You can email the technical director at: jadey@abycinc.org

What you need is a thermostatic tempering valve on your hot water heater and you can easily install one. Your situation is not uncommon and the ABYC is looking into this but they do need to hear from boaters who have this dangerous problem in order to get any safety issues like this through the PTC. You also may need to replace the check valve...

kloudie1 · May 6, 2012

Gettintheere, having the tank that hot with a proper tempering valve makes a smallish tank seem to have much more hot water than it actually does.. Because the water inside is pressurized, there is no chance of it boiling and the tank does have a safety valve .. shouldn't be an issue .. but the very hot water at the tap without a tempering valve could be a problem.. Most boats piping is not even rated to cary that much temperature at the normal fresh water pressure.. Like Maine Sail says, seems to be a disconnect at the ABYC on that issue.. If the tanks were all sold with the valve, the problem would be reduced considerably .. This can be done for less than $100 if yoiu plumb it yourself.. http://www.ebay.com/itm/TACO-508-4-...A%2BFICS%2BUFI&otn=21&pmod=261014778210&ps=54
These valves work like a check .. until there is demand, there is no mixing .. no hot gets to the cold side..