|The space where the heater is now sitting was the place designed for the water tank|
|after plumbing and electrical is complete will complete cabinetry underneath sink|
As you can see in the picture below there is an electrical junction box mounted between the wall studs. This box is for the service of the 120 VAC instantaneous hot water showerhead. Also above that is the switch that runs the 12 VDC waterpump. This allows me to turn off the waterheater electrical supply just prior to turning off the pump to ensure I do not have a dry element and ruin the showerhead.
Risky facets I agree...but options are very limited in North America when it comes to 'hot water heaters for campers' unless you want to take up a lot of space, spend a boat load of money and then whine about how much you just spent. This particular unit I installed - Marey Tankless point-of-use, water heater showerhead- is not even offered on the home range, these come from Peurto Rico. It will be served by a 30A Ground Fault Circuit Interrupter breaker in the panel.
A peek underneath the sink shows where the incoming water line will be connected and the sink drain/vent.