Tech article by Marlon Allen (NOTPRETTY)

The heat exchanger: I found this at a refrigeration supply store. It is called a ½ ton coaxial coil exchanger. It is a tube in tube design and is very affective. In fact, it may be too good. The water coming out of my showerhead is pushing 112 degrees. For testing, I filled a huge cooler full of ice and then added water. Water was under 40 degrees and at the shower end…perfect shower water. It cost me $56.00
Hook up the exchanger by simply tapping into the heater core lines. There are heater control valves to assist you with this. The water from the radiator should flow in the opposite direction of the shower water. This gives better heat transfer.

As you can see in the picture I have added a compression fitting to connect to the line that goes to the showerhead. Compression fittings work, but I would suggest something that you can solder on for less chance of leaks. Get one end threaded so you can disconnect the line easily. It is 3/8th outside diameter (OD). On the line coming in from the pump use a hose clamp. The dimensions are as follows. The outside diameter of the coiled part of the exchanger is 6 inches. The ends sticking out for the connections are about 3 inches. Sitting flat the entire exchanger is about 4.5 inches tall. You can see one of two mounting holes in the center of the coil. Laying flat on the drivers-side inner fender with the pump mounted next to it is a very good fit. Might be a tight fit with the power brake booster, but I think it should still fit. One more note on the exchanger. If you truly want an exchanger designed for domestic water there is a version made of nickel…or dipped…or something like that. It is resistant to corrosion. It doubles the price though and my thought is this…Let it run for 20 seconds and then start showering. Any residue from the last shower will clear. Also, the river water is probably not that clean anyway.
In the below picture you can see the how I connected the exchanger. I by-passed the heater core entirely for my testing in this picture. In the picture you can see the output (normally to heater core) coming off the water pump going to the exchanger. The return line on the top going into the intake manifold. ¾” heater hose is cheap and can be found a Home Depot. 5-6 bucks include hose clamps

In the next picture you can see the entire set up. The pump is a Flowjet marine application pump. Another good pump is a Shurflo. It has a bit better water lifting capacity, but he Flowjet is a bit quieter and quick disconnects the hoses. Shurflo might do that too…not sure. Whatever you get you want self-priming and at least 3 gallons per minute…and 12 volt. Either pump can lift water 4 feet easy. The pump (Camping World - Flowjet Quiet Quad II) costs $65.00. Showerhead at Home Depot…$3-4 bucks. White plastic hose is domestic water line and is very cheap per foot…I think $.12 cents per foot.

Here’s a good look at how I would put it in. The exchanger would need to move a bit towards the fire wall and to the center to clear the steel hood cross member when closed. I’d say 1 inch each way is all. I haven’t bolted it down in this picture. If you spend some time routing lines, setting up quick disconnect, wiring in a switch you’ll have unlimited hot water virtually anywhere. Please be careful not to burn yourself or a little one. The safest way to operate the system is to start it and don’t stop it. If you do stop it, start it again point away from you. The pumps have over-load switched built in and can stop and start, but shouldn’t unless it clogs or the pressure on the pump increase for some reason.

Steps to running the system: position the vehicle so that the water source is as level to the vehicle as possible…above is good too…this just takes pressure off the pump and increase pump life. Again, a 4-5 foot lift will work. Start the vehicle to warm as you hook up the lines. It doesn’t have to be HOT to work. Turn the switch on and leave it on. Find the distance from you to the showerhead that is comfortable and start scrubbing up. Please use biodegradable soap. I fish and want them healthy too. Click here for a fairly compact lightweight shower enclosure. ENJOY!