On Board Hot Water Shower

File this one under luxury addition, but having a hot shower for camping or after scuba diving is just nice.
I'm looking forward to showing this mod off next week when I'm in Arkansas scuba diving. First some links.

Shower Information

Off-Road.com review of R&M Specialty Products Camp Shower
A home build heat exchanger, that was never finished
Another User of a R&M Shower
A list email on making a heat exchanger
A write up on the Twine Aussie Vehicle Shower
Twine Shower Homepage
James Yatras' Shower
Glind Hot Water Systems

The first thing I noticed about all the showers out there is that they all have the same basic components. An RV water pump and a heat exchanger. The next thing I noticed was the price! $350 for a shower is a bit steep for me to slide past the wife. I determined to do a budget install. First I went to the local RV parts store. There I bought a SUREflo 2.6GPM pump. It has a built in check valve, a 2 year warranty and is 12Vdc. Next I had to hunt down some Copper pipe. 2-3" copper pipe is hard to find. It's usually used for commercial applications, and the only dealer in town that carries it that large sells it in 20' lengths. I called around and bought two one foot lengths of 2.5" copper pipe. I picked up a couple of 2.5" sweat caps from the local plumbing supply house. These aren't cheap - $9 each.
Drove to Lowe's last night and picked up just about everything else I need. I forgot to get brazing rod and some gas for my mapp torch.
Heat exchanger Concept:
This is a concept drawing I made up of the heat exchanger. There will be a few more loops in the internal pipe, but this gives a good idea. I'm still undecided about which chamber the coolant should go through. There will be less flow restriction if I run the coolant through the outer chamber, as I can braze on the 5/8's barbed fittings pretty easily. Also, the pipe is 1/2" in diameter, as are the water lines. I think it will heat it more efficiently and be less likely to freeze and suffer from water expansion if I run the coolant through the main chamber. The advantage of running the coolant through the pipe will be less opportunity to burn your hand on the exchanger.
Here's a hook up diagram of the entire system. It makes sense to put a waterproof switch at the hook ups. Note that I did *NOT* use a showerhead with a turnoff. That may be handy in concept, but keep in mind that when water sits in the exchanger it will become hot enough to cause burns. My family isn't always the most cautious, so I've purposely left out a cut off at the showerhead to prevent accidents.
I've got the heat exchanger mostly made. Initially I wanted to braze two 5/8" barbed connectors to the end caps for the coolant to run through. After trying out two kinds of rods, one for copper and copper based metals, one for general metals including copper and neither bonding to both the copper and the brass, I gave up and soldered them together. It came out fairly sturdy, and looks just like what some others are selling so I'm going to give it a shot. Once I pick up a 5/8" drill bit, I'll finish up the heat exchanger and mount it under the hood just above the valve cover on the firewall. The next challenge is mounting the pump. For the meantime, I may just dig it out with the hoses whenever I'm ready to use it, but I'd like to get it permanently mounted under the hood somewhere.
The exchanger is now mostly complete. All that remains is to pick up a 5/8" drill bit, some heater hose. Then I'll need to drill the caps for the oulet pipes, solder on the end caps and to fabricate some clamps to mount the exchanger with under the hood. I managed a total of 5 lenghtwise runs through the exchanger with the 1/2" pipe. This was the exact maximum I could fit.
Here's the end view. You can see how tight the fit was, I had to mash on it just a bit with the vise to make it fit in the pipe since some of the lead bonded the pipes toghther just a bit. Next I'll just need to finish up the caps.
Here's the Heat exchanger completed and installed. The water lines are 1/2" flex hose from the hardware store. The Heater is 5/8" heater hose from the auto store. I removed the line from the front of the engine, where hot coolant exits the thermostat housing. I attached that end to the heat exchanger and added a new line from the exchanger to the thermostat housing. This way the hottest coolant goes into the exchanger first. It shouldn't adversely affect the heater in the winter, but should heat the water nicely. I field tested the system using lake water down in Arkansas to SCUBA dive. It made the 69 degree lake water into a nice warm shower. Not quite hot, but a good comfortable temperature. The water pump performed very well, since it sucked the water up from a 4-5 feet below the jeep, up to next to the battery, and out the shower line.