I know, I know lower heat? Well the reason I thought of this was to use a hydraforce sprayer. I have a high heat tm and wanted a quick way to lower temps to spray carpet. This is my idea. place a solenoid valve inline direct form the pump to the pressure line right past the last heat exchanger. When you want cooler water activate the solenoid valve. This should mix cold water with your heated water and cool the solution down enough to spray. This could be activated by a keychain remote from inside the house if you get fancy. This could also be a way to avoid a exhaust diverter valve. Place a temperature sensor after the heat exchangers. When it reaches a certain temp it opens solenoid valve and mixes cold water with the heated water to bring the temps down. This will help even out temps and will conserve the hot water from the heat exchanger because water will be traveling through it slower. I'm open for some brilliant minds to punch holes in my theory, thats why I'm posting. So whatcha think?