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OBHS - On Board Hot Shower

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normally I don't post up something until it's finished and most of the bugs are worked out. this time I figured "oh what the heck"... lets let you laugh and cry along with me on this mod! so, i'll be posting as i make progress and you can jump in with criticisms and "I told you so" remarks right from the start! :D


i purchased a coleman hot water shower system when i first got into doing expedition type trips, and took it on the first one... that was the last time i ever used it! it was really an awesome thing on a cold morning, but took up way too much space and took a little setting up. it's still my favorite device within that genre (compared to the Zodi system). here's what i'm talking about:




ever since realizing i didn't want to haul that really, nor set it up, i started dreaming of an on-board-hot-shower system like the popular Helton, the R&M, or the TWINE. these systems use a heat exchanger to take the heat from your radiator fluid and give it to the fresh water you pass thru and thereby give you a vehicle based hot shower.


the first thing you notice is that the systems are around $300 to $500 dollars, with the heat exchanger being the main cost. that price tag moved the whole dream to the back of my mind.


however, recently G&D got a shower tent and got me started thinking about my old un-used shower tent and with my mom and cousin coming on their first expedition with me this month, i started looking into the on-board-shower again.


what i found out is that heat exchangers are more common now and can be had for under 50 bucks... this is due to them now being used in quite a few application (even home beer brewing) as well as technology just always evolving and becoming cheaper. i'll get more into plate versus coil style exchangers later.




now with a $45 heat exchanger, some hose and fittings, and a battery powered shower like the Stansport or Zodi, you can have a working system for under a hundred dollars.




but of course anyone that knows me knows i wouldn't be happy stopping there! details to come...

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so here's where this is all headed, when done the system should work like such:


- only have to store a couple small hoses and shower head inside the jeep, taking up minimal space


- when ready to shower, process should be:

1. pull out a water filled jerry can.

2. pull out the 2 hoses.

3. connect one hose to the jeep and drop other end into the jerry can

4. connect the other hose with to the jeep and run the shower head end into the shower tent

5. flip a switch to turn on the entire system

6. optional: start the jeep and let it idle to heat the water. however, on hot days, be able to bypass the entire heat exchanger for a cool shower


- should have an on/off on the shower head so that you can conserver water by wetting down, turning off shower without reaching outside of the tent, soap up, turn back on shower without reaching out of tent and rinse off


it's important to be able to easily conserve water since most of my camping is in the desert and the only water is what you bring with you. however, the system should also be stable for long showers (if there is a nearby water supply).




(image from "unwiredadventures" on expo portal, and big thanks to him to for the mix valve idea too)

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item #1: water source


the first idea was to have and on-board water source... a permanent or semi-permanent tank. i love the idea of the Front Runner Footwell tank: http://www.equipt1.com/companies/Storage%20Solutions/product-fr/130866-water-footwell-water-tank-40l




it keeps the water down low for your COG and seemed like a perfect solution. unfortunately, it doesn't quite fit the center-hump in my WJ... perhaps one day i'll have a custom tank similar to this made.


Front Runner also makes a wedge shaped tank that would be perfect behind the rear seat, but it's just a little to big to fit with my spare tire... maybe one day if i have a rear tire carrier, then i could go this route.




i just couldn't find the exact right semi-permanent tank... but i have not abandoned the idea completely yet. however for now i decided to just use a couple Scepter Plastic Water Jerry Cans. i already had a half-height (10L) one that i really liked, and so i picked up a couple of the full size ones (20L). I got desert tan because that's what i could find at the time. i think they where about $30 each.




this means i have the extra step of deploying the water can instead of having a tank always hooked up, but i can live with that.

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item #2: water flow


having a source for water, i then needed to decide how to move that water. the little battery powered options that i mentioned in the first post just seemed like extra hoses and wires and batteries going everywhere to me... i wanted a more integrated and simple-to-use solution.


i wanted to be able to turn off the shower head from within the shower tent without reaching out to have to flip a switch and/or also turn a valve.


i looked at different ways of doing a pump with some sort of pressure overload valve directed to a recirculation type system so that if you just had a valve on the shower head and turned it off, the pump could keep pumping without burning up. eventually though, i found out that RV freshwater systems already had all this figured out and an RV freshwater pump would do the trick.


The RV pumps already operate on 12V DC, they also have a built in pressure sensor so that they come on and off whenever there is demand for water without you having to flip a switch or do anything other than turn on and off a faucet/shower/etc. Most of them can also self-prime and many can run dry for a while without burning up. Seems like there's always an answer already out there, just knowing where to look is the real challenge!


ShurFlo and AquaJet seem to be the most common pump makers, there are a couple more though. it also seemed from scouring the web that the ShurFlo Classic was the tried-and-true, middle-of-the-road performance/cost pump. It's been around for a while and you can buy parts to rebuild it instead of having to replace it depending on what breaks. so that's the one i chose. i found it for about $65.




it's a little more powerfull at 2.8GPM than i need, but has the ability to dry prime from up to 6 feet below it and can push water above it 12 feet. i can limit the flow with an adjustable shower head to keep from wasting water.


the only issue i saw is that it is meant to be mounted inside an RV and is not sealed or weatherproofed. that said, it doesn't appear to be particularly wimpy either. i found other people on the net having mounted them outside in a semi-protected area and not mentioning problems. shurflow does make a smaller pump called the Aqua King that is somewhat ruggedized, but it's specs aren't as good so i decided to just risk it with the Classic pump mounted in the engine bay. i did mount it as high as possible as i'm sure it wouldn't like being submerged in a water crossing!


i did look around and found a couple places that i could have mounted the pump inside the WJ without really intruding on cargo space, but that would have meant plumbing in and out of the cabin and eventually i decided on just putting everything up front for now for simplicity (since the heat exchanger has to be plumbed into the front no matter what).


Shurflo also makes a little pre-filter for the pump to make sure you don't get any debris in the system. this was only a few bucks.




so the first task in actually making this system was to install the pump. i tried several areas and finally decided on just behind the air box. this required moving one emissions thing-a-ma-jiggy (the evap purge solenoid actually). a piece of bent aluminum, a few holes, and a couple self-drilling screws and that part was done. oh, i did have to get a few feet of some vacuum hose too. total cost for this was a few bucks.




next step was making a bracket for the pump to sit on. this required a trip to ACE for some steel. then some bending, some drilling, some screws, paint, and there's you're bracket. total cost, another few bucks plus time and gas for the hardware store.




here's the pump, pre-filter and hoses all installed, and then a shot with the air box back in place... everything just fits! though i did make sure that with the pump on and vibrating, it doesn't hit or rub anything.






you'll notice i decided to go with the braided flex pvc for connections and brass fittings. i decided on 3/8" ID hose as a compromise... all of the components in my system (the pump, heat exchanger, some other things) all used 1/2" threaded connectors and i originally was going to use 1/2" hose but decided that was overkill and would be hard to route, and I thought 1/4" might restrict flow too much. I decided on brass fittings with barbs and hose clamps because i didn't want to have any custom crimped-end-fitting hoses made, and i don't like tightening down hose clamps on plastic barbs... just doesn't give me a secure feeling. I also considered using car heater hose instead of PVC, but decided if i ever do a semi-perm tank, i might want this system to stay drinking water safe (i.e. might have a faucet in the back of the jeep one day).


the biggest issue so far has been going to the store endless times for fittings... you think you have what you need all planned out, then you find you need a 90* somewhere because a straight nipple doesn't fit... then ACE can only do it in 2 fittings, so you go to Grainger to get a single fitting that will work.... only to change the mounting later and start all over with what you need!!!! arg!!!

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that's it for last weekend's work, stay tuned for this afternoon's accomplishments...

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Looks good to me K. I once had the idea of using the windsheald washer in the TJ as an on board shower, but you would have to take a shower as soon as you pull into camp because it only stays hot for a few hours. George:cool:

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Looks good to me K. I once had the idea of using the windsheald washer in the TJ as an on board shower, but you would have to take a shower as soon as you pull into camp because it only stays hot for a few hours. George:cool:


thanks G.


yeah this whole idea has been done by plenty of people before, just documenting my particular try at it for others to learn from. i've got some thoughts on how to improve on the typical system that i've seen as well.


i hadn't heard of the windshield washer idea, that's not bad other than it just being a small amount of water (thought you could put in a bigger tank). some people with manual trans have also used the auto trans cooler lines in their radiator to heat water, but that isn't very efficient and produced kinda weak results from what i read. then i saw a couple posts out there about people thinking of wrapping coils of tube around their exhaust to heat water, but didn't see anyone do it successfully.

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i'll bring extra water for a personal test of your OBHS system next time out on the trail.:D

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item #3: hot water


heat exchangers pretty much come in 2 flavors, a tubular or plate design. the tubular is one big tube with a little spiral of small tube inside it, usually made of all copper. they are low-tech and high-durability. the plate design is newer and is supposedly much more efficient at transferring heat, they are also quite a bit more compact. the only drawbacks of the plate design are that they are more restrictive and require a little more pressure. also one person on another forum questioned their durability in a vibration prone environment such as a vehicle. the traditional car hot water shower makers are all the classic tubular design.


plate design:




i should mention that you can make your own heat exchanger if you have some patience and brazing skills. here's one example of a homemade one:




the newer plate style are the ones you can now pick up for near $50, and so that's the route i went.


the next question was how many plates... the more plates the more heat transfer, but the more restricted the water is. i found one person on a forum claiming his 10 plate was plenty hot, and another person on another forum recommending a 20 or 30 plate. it does also have to do with what temperature your vehicle runs at. since my WJ normally operates at 210*, and having heard the plate exchangers are so efficient, i decided to try a small 10 plate one. i'm happy to report that upon first test, it's plenty hot. i picked it up for $45 shipped.


usually you install these in the heater hose circuit. in older vehicles, water only flows thru the heater core when you turn on the heater, so you want to install your exchanger in parallel with the core. on most modern vehicles though, water flows thru the heater core all the time, so you can install in series. most people recommend installing on the return line so that you don't affect the cabin heater's efficiency, so that's what i did.


i mounted right next to where the heater hoses enter/exit the engine, on the frame. i had to make a simple bracket out of some aluminum sheet:




i cut 2 short pieces of heater hose in half length-wise and used that as an insulator between the bracket, frame, and the exchanger. hopefully this takes care of any of those concerns about durability in a vibration prone environment.




make sure you have your hot water and your fresh water flowing opposite directions in the exchanger for maximum efficiency.


you'll notice a big brass thingy in the first pic above... i included a check valve on the fresh water input to the exchanger to keep hot water from flowing back into the system. this is because i have a "T" fitting after my pump, where i am directing cooler fresh water to one outlet and hot water to another and didn't want the hot water to mix back into the cooler water. i'm not sure this step was necessary, but i already bought it so i put it in.

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item #4: regulated heat


the first trick i saw from reading other peoples versions of this was that you needed to include a "Y" valve or faucet style mixer to mix fresh and hot water to get the temperature you want because you can't rely on the temperature coming out of the exchanger to be just right.


then i also read that a common minor complaint is that when you have the system not moving water (like while soaping up), the water sits in the exchanger and can get scalding hot. therefore you have to remember to point the shower away from you when you first turn it on so that you don't actually burn yourself... this of course is wasting a tiny bit of water but also a potential safety issue.


only one person i've seen so far discovered the anti-scald device, and they are therefore a genius in my book! the anti-scald device, or thermostatic mixing valve, is a magical thing that takes hot water and cool water inputs and outputs the hot water regulated to a maximum threshold. i.e. if the water coming in gets too hot, it mixes the right amount of cool water with it to produce a safe, non scalding output.




you can buy these with a preset max setting to keep you safe. however i found out you can also get them in variable versions that allow you to adjust the output temperature with a plain knob... so that's what i went with. this way instead of needing a preset anti-scald device for safety plus a "Y" valve for personal taste temp setting, i could just use one variable thermostatic mix valve to set temperature and keep it.


these devices can be costly, but i found a deal on ebay of some unused open box ones for $25 made by Watts. the one i got is a little bulky but since they usually cost around $75, i can deal.



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