Passive Solar Hot Water Heating

[Roadtripp]

Now that solar electricity panels are cheaper it makes sense to use electricity. Space and weight are a concern also. Installing only one system that does hot water makes sense. However I haven’t given up completely on passive solar hot water. Especially if camping in one place for periods of time. 
 I’ll share a inexpensive passive design I saw for solar showering and domestic hot water. They used sections of plastic solar swimming pool heaters. They cut a 20 foot pool heater into 5 foot sections. Four solar showers were built on their property because they have large gatherings of people camping on the land in Summer. 
 They cut a groove into a plastic header pipe and used some type of high tack goop adhesive to seal the plastic pool heater into the header pipe. The water thermosyphons into a tank. It worked great for them and didn’t cost much. 
  I have enough pool heaters collected to make several hot water systems. Is it worth hauling the stuff around. If the tank and collector is attached to the roof that would help.

[Roadtripp]

I will ad that I have used a solar shower bag and will keep using them on occasion. I’m thinking about ways to make larger volumes of hot water.

[Flying kurbmaster]

I wouldn’t carry all that stuff around with me, if you plan on showering a large number of people you would have to have a good water source. I use one or  two square BLACK plastic kitty litter buckets, I set them out in the sun in the morning have a shower around dinner time. In the summer this works well sometimes too hot, when it gets colder I simply boil a kettle and pour it into one of them to warm it up a bit more. I used to have a 12 volt submersible pump with a shower head on it but when it broke several years back I simply used one of my pots and dip it in and pour it over myself outside, that works for me. I think vandwellers tend to put too much thought and effort into showers, they are not very practical in small vans especially inside, they also use up a lot of water. A warm sponge bath works well too, especially in very cold weather inside the van.

[Motrukdriver]

https://www.rei.com/blog/camp/diy-car-to...amp-shower

[Roadtripp]

FK. I hear you regarding water and overthinking water systems. Guilty as charged. Your system is about as elegantly simple as a pumped system can get. Few headaches or risk of freezing.
Having said that Mo added a link in post #4 to a air pressurized solar water heating tube that fixes conveniently to the roof. I’ve tried to build something similar but have not used it yet. The Motorhome roof is very tall. Getting water into it was a issue the way I designed it. I wanted to to pump it full or fill it from a pressurized faucet. My van rack is also tall for dumping jugs of water. I planned on having a 6’ washing machine hose hanging off the back of the van and motorhome but didn’t get the opportunity to use it yet.
A friend in Florida built a similar 4” ABS plastic solar batch heater but he put a 2’ riser on it so it could store more compressed air. He said that it worked well. The pressure lasted a long time compared to a tube with no riser. And he wouldn’t be tempted to pump excess pressure and possibly rupture the tube or cause a leak. I’m not sure what air pump he used but think it was 12 volt electric. I saw a thread here about air compressors. A better 12 volt compressor is on my wish list.
He built a miniature pea pod trailer and the abs was underneath so did not get solar heat gain from the sun. But Florida is relatively warm and a cool shower is nice there. I’m always looking for more hot water in the Pacific Northwest lol. The tube location underneath is easier to fill.
I saw a van with a full loop of 2” abs plastic going all the way around the roof. It looked good I thought and the owner said it was a decent shower. It had a Shrader valve for pressurization.

[TrainChaser]

The problem with a system like that rooftop one is when the water gets too hot, and there's no way to add cool water.

[Motrukdriver]

If you wanted to go all solar you can get a small electric water heater (25 gallons or so) and replace the 120vac element with a 12vdc element and use that as the load dump when your battery bank is fully charged. Insulate the tank really good and you'll have warm water at least until the element kicks on for hot showers in the afternoon. Need a bladder tank with a check valve to keep the water system pressurized and full of water but it can all be done from inside your living space with a hand pump for air pressure and foot pump for water filling. Set the max temp on the element thermostat to what your minimum comfortable shower temp would be and you are good to go.

[Abnorm]

25 Gallons !!!...…...I think Jim uses a 12 volt HotRod in his 6 gallon RV tank...……….

[Motrukdriver]

Yeah, that might be much... How about this one?

https://www.supplyhouse.com/AO-Smith-EJC...gIS7fD_BwE

[justjim]

My Hott rod is in a 6 gallon RV water heater. It is 120 Vac and pulls 450 watts for two hours taking the tank from cold to 150*F.