Simple passive solar water heater

Way over thinking this and adding considerable work.

If this is to be a "mobile" system (campground to another campground) you will have to fill and drain a lot of water then figure out how to haul a drum around..

Lots of "overhead" trying to heat all that water above ambient air temp, will take considerable amount of time to see any benefit, especially if you are filling from empty with very cold water.

Drum of water will cool down considerably when the sun goes down, especially during winter nights, even in the south..

What you are trying to do is called "batch" solar heating, which can work but typically it is done using a solar panel and a well insulated tank.. in the daytime the water is circulated through the solar panel, heating the water in the tank. At night, the water is not allowed to flow through the solar panel (flow through the panel would release the stored heat back into the outside)

I suspect, you can do the exact same thing with just a length of black pipe laying on the ground or even laid out in a couple of rows on the roof of your RV.. Some folks have just coiled up black pipe into neat coils with pretty good success.. Depending on the size of coil(s) you make it should be easy to store when traveling!



Simple, yet very effective without all the hassles..

For more great ideas go to BUILD IT SOLAR

What is the hoped for outcome of this? Is this for hot showers, for dishes, for on demand use at all times?

THE surface area is the key to getting effective temperature rise and the height of the containment is the key to getting improved pressure.

Knowing what your planned uses are will help us offer better suggestions for success.

Old-Biscuit wrote:
55 gallon barrels are 'containment' vessels built to HOLD fluids.
They are NOT designed for Pressure

Yep, 40 psi on the base of a 2' diameter drum will exert around 18,000lb of force on the bottom of the drum.

Short of building a custom extremely strong drum, you simply aren't going to be able to pressurize it.

Two viable solutions:
- Raise the drum and let the "head" generate pressure (this is why water towers are TOWERS) but probably not practical for an RV as it needs about 92' of height to generate 40 psi.
- Add a pump on the outlet pulling water from the unpressurized barrel.

Bigger issue is a large barrel will take a long time to heat up. You need lots of surface area to heat quickly.

As I read this I am trying to figure out the plumbing. Once you get the water heated in the barrel - how will you get it into only the hot side of the camper`s plumbing system? Every camper I have ever seen has a single inlet for city water. They don't have separate inputs for hot and cold. Are you doing a mod to the campers plumbing?

Elevation is the key to regulated pressure without deforming the drum. Each foot you can elevate the drum above where you intend to send the water will give you .43 psi.

Swell1 wrote:
How about putting a 12 volt pump in line. Let the barrel gravity flow to the pump and let the pump build your pressure.

This. You are trying to build pressure on the wrong end.

You don't need to pressurize the barrel. Use the pump in your RV to suck the water from the barrel.

bpounds, 40 is good but if a lower value can feed the shower appropriate, I'd be okay with it. but 10 just isnt cutting it.

Big Katuna, man I have seen things about that online. I was hoping to start out smaller and simple and build it up if need be.

Swell1, that's a good idea but I was hoping to stay away from electricity on this project, my camper does have a pump on it I might use.

Afidel, that wort chiller might be the best way. I especially if I elevate the coiled part to the higher (warmer) part of the water. And I believe there are specific liquids for that stuff that hold their temperature longer

after googling a bit it seems like these barrels are infamous for not holding high psi and potentially posing a hazard if psi is too high

55 gallon barrels are 'containment' vessels built to HOLD fluids.
They are NOT designed for Pressure

Maybe try a wort chiller in the barrel as a water-water heat exchanger.