I have a marathon water heater... currently the recirc pump feeds into the drain line (this is how plumber installed). Based on how a marathon is designed (and this return line configuration) it would seem to me that this "cooler" water will be pumped up from middle bottom of tank.. (how high it goes, I dont know).. on a conventional water heater, the "cooler" water would be pumped in sideways at the bottom and be more apt to stay at bottom.. Do you think that the "cooler" water being pumped upwards would cause the water heater to run more often therefore resulting in a higher electric bill? I'm thinking that perhaps I should reroute the return line to go into the cold inlet pipe instead... your thoughts?