When it came time to choose what water heater system to use in the camper I quickly realized the shortage of choices. I would have loved to have installed an in-demand unit remotely but simply did not have the remaining monies at this point in the build. Plus, I really did not have the space to mount one anyway, after making appropriate arrangements for a larger water tank. I guess I could have mounted one on the exterior wall adjacent to the sink I suppose but the cost was the limiting factor.
I had seen an 'in-use water heater shower head' years ago and began a search for a reputable supplier. I ended up landing on the Marey Heater Corporation site, this firm is located in Peurto Rico and offers the 120 VAC in-use water heater, shower head. I was a bit concerned having such an arrangement- wet environment, powered unit in the shower- but there appears to be safeguards (insulated housing). I plan on installing a ground fault circuit interrupter (GFCI) on this circuit. One should never have any type of electrical install that serves a wet area (sink, countertop, exterior app) without one. Matter of factly it is a National Electrical Code mandate across US....well yeah- 'national- US..duh!'--lol. A 30A GFCI circuit breaker will suffice.
I understand these units are commonly used all throughout Peurto Rico, various parts of Mexico and perhaps other portions of Central America within their dwellings and commercial buildings.
My plumbing was certainly not the neatest install, but functional. I have a switch for the shower head and another switch for the water pump. I can turn the power off to the shower head before I disengage the pump, thus preventing a dry element incident.
The piece of angle the shower head is mounted to is for rigidity while in transit because the shower head is forward heavy. The surface mounted plumbing allows me to remove the unit should it ever need replacing. Was not enough room in my wall studs for the fitting arrangement and it was O'dark-30 when I was working on this, no stores open and I needed this baby in. Anyway it's not a photo booth, just an area to wash after a day of field research.