On Aug 2, 7:29*am, Theo wrote:
Recently replaced old electric water heater with a 40-gallon SuperStor
running off oil furnace. It now overpressures and vents several times a
week. Feed pressure is about 30 PSI. A cheap max-indicating pressure
gauge confirms that pressure jumps whenever a lot of hot water is used,
though it doesn't always reach the 150 PSI needed to vent.

I've tried to convince the installers that 40 gallons of water expanding
from 55F to 140F is going to strain the pipes in this small house, and
that some kind of expansion tank (like the one in the heating system,
right next to the SuperStor) is needed. They think I'm nuts.

Can anyone here offer relevant experience or practice?

Thx-

Theo

Dont you mean it runs off your boiler, what vents, the boiler or
heater, On my old pipes I would never let them get over 75, 150Lb ! I
think you are crazy to run it at all. The installer was a hack if it
actualy goes to 150lb. Whay do you even need 140f water, lower it now
to the lowest temp you need to take a hot water shower, with no cold
added. for me thats 95f, it will lower pressure before you break alot
of stuff. Pressure should not be more than incomming. Also you now run
the boiler to heat water in summer, likely that will cost you alot
more in summer.