Quote Originally Posted by 996scott View Post
ok, makes sense. 1 more question if you don't mind. So my thought is that in order for that extra heat exchanger to work, the hot coolant that comes out of the engine would have to be moving/flowing through the hose/heat exchanger, meaning that the heater would have to be turned on. If the heater isn't turned on then there isn't any hot coolant to warm up the water going to the shower. In my mind it seems like if i add the extra heat exchanger then i would have to have the heater turned on when running the shower to get the shower hot. Does that make sense?
Your circulation pump for the heater is always on with the engine on (it's tied to the fuel pump circuit) so when you turn on the heater the only thing you're turning on is the blower fan.
The coolant is running through it all the time in a constant loop when the engine is running.
The shower setup would be the same, coolant always flowing through the heat exchanger but no hot water until you turn on the shower pump.

Something that just occurred to me is that that first burst of water when turned on will have been sitting in the exchanger so it will be quite hot (engine temp most likely).

May not be a great idea afterall, i'd hate for a kid to turn it on and get blasted with a seconds worth of 160 degree water.