Custom RV hot water set-up consideration

[j-c-c-62]

Is it feasible to use RV engine hot water to preheat potential shower/sink water while driving?
Seems biggest hurdle would be to not overheat the water and or regulate the temperature somehow tp prevent scalding?
Seems like free heat. I am personally averse to using propane on board for stove or hot water.
I likely would have a connected separated metal insulated tank fed off main freshwater tank for this solution.
I also would have a small capacity point of use electric water heater as back up in series.
Electric is limited as solar/batteries are my main energy source with the RV/.

 

[Cop car wagon]

Marine water cooled exhaust manifold.
Fresh water in/out, while you shower.
Don't know if driving with it empty of water would be a problem.

 

[j-c-c-62]

Hadn't thought about using the exhaust.
Interesting.
It's a 5.7 Cummins Turbo, BTW

 

[Tony Tee]

My dodge van has a manual transmission. So I used the transcooler in the radiator to heat my water. Just turned the circulation pump on for 30 minutes while driving and it warmed up a 35 gallon water tank to very comfortable hot shower. No problems from Florida to Alaska and back.

 

[bm02tj]

A plate heat exchanger an aquastat controlling a 12 volt pump relayed off ignition

 

[RemCharger]

A plate heat exchanger an aquastat controlling a 12 volt pump relayed off ignition

An on demand heater? That's what I was thinking

 

[BMosely]

Route your hot water under the RV to the outside wall and install 2 hose bibs. Hang this instant hot outside and connect to the bibs. Turn on and have endless hot water. This will keep the propane outside which is what I assume your propane issue is. It has a battery electronic ignition that is self contained.

 

[1967coronet]

Years ago I pulled food grade tankers for ADM. Soybean oil would gell if not kept warm in transport.
Our tanks were insulated plus had lines between the inner and outer stainless skin full of 50/50 coolant that ended with quick connects on the front of the tank.
These plugged into the trucks coolant system with quick connects on the back of the sleeper.
So yes your idea will work, as far as temp control that will involve length of line , outside temp.
I would add scald guard faucets.