valves are a must. You most likely will not be able to shut down the lp heater., The Kuuma is a helper coil not a heating coil. keep in mind if your tank was 120* and you took a 10 min shower at 3 gal a minute, you just mixed 30 gal of 50* water into the 50gal you have left. It takes a long time to heat an 80 gal tank via thermo syphon. Get a hp water heater tied in to that system and you can get the savings your looking for.
yeah, I am guessing I won't be able to take my heater out either, but it won't hurt to try
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