Having an onboard shower is great, especially for overlanding when you may go days between towns. And if you like going out to remote areas camping for a few days, boy does a good shower make all the difference. Using the existing energy source as your vehicle engine is a solid idea, especially if that vehicle is more or less your dedicated expedition rig. Here's my setup:
This is a 30 plate heat exchanger that I mounted under the hood, inline before going to heater core. I think 30 and 40 are far too big. 20 would probably be perfect. But hey, better to be too hot than not hot enough.
Got two hoses coming up to shower, cold line that tees off before going into heat exchanger, and hot line coming from heat exchanger. They go to a thermostatic mixing valve that I had ground down the inside of the adjusting knob so it doesn't lock and you can easily adjust temperature during shower.
Had to add a shower curtain of course, the ladies wouldn't have it any other way. I just bent some 1/2" EMT with a pipe bender and it sits into two pipe straps. I found a 9' shower curtain on Amazon. Apparently, most shower curtains are only 6'.
I store the curtain rod on the roof around the spare tire.
Here is the on demand pump and hoses. The way it is setup I can can pump water out of or into the onboard 18 gallon tank under truck or the 2 or 3 5 gallon Specter cans on the back. I also have a longer hose and large particle filter for pumping water out of creeks or lakes or whatever. Inline with the pump is a smaller particle filter.
This is the ABS tank for onboard water storage. Since it is suspended from underneath the bes of the truck, I welded up an aluminum cradle from scrap laying around the shop.
Water coming from heat exchanger was about 160 degrees, so the mixing valve was a must. After mixing balve, the water was a nice 111 degrees.
Boy, it hits the spot on those below freezing days...
And it really helps women tolerate coming on our crazy adventures!
