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Valve's Closed, pipe is still hot?

Sbecker Member Posts: 1
We have a superstor contender indirect tank off an oil furnace. We had trouble with pressure and the hypothesis is a pin hole in the coil/heat exchange. Longest story ever short.... We closed off the in and out valve from the boiler to the hw tank.  Two elementary questions... Why/how do we still have hot water? And should the pipe *after* the closed valve from the boiler to the tank be hot? The pipe from tank back to boiler is cool. 


  • hot_rod
    hot_rod Member Posts: 22,468
    A picture might help see what valves are off.
    The valves may not be shutting off 100%
    The pipes are conducting heat
    The tank may stay warm for a day, depending on how much DHW you use
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • mattmia2
    mattmia2 Member Posts: 9,942
    Which valves are you shutting off? The coil from the boiler connects to a connection about 1/3 of the way up and to another connection directly below it near the bottom of the tank and the DHW connections are inlet near the bottom of the tank and outlet near the top of the tank.

    You could also test for the coil leak by turning off the domestic side and letting the pressure out of the dhw system. If the coil is leaking and the valves aren't holding to the boiler you will still get a drip to a trickle out of the dhw.