In this video I would like to demonstrate the design, construction and usage of my DIY solar powered, pressurized, roof top water heater and shower.
I've been looking for a portable hot water heater for traveling and camping for quite some time. I looked at both the solar powered gravity fed bags systems as well as the propane powered systems. However the solutions were either inadequate, took too long to heat, too expensive, or too bulky.
I discovered one solution online that used an aluminum tank mounted to roof racks. It was pressurized using a battery powered air compressor. This looked ideal however the cost was $300 plus $60 shipping plus $20 import duties and taxes. This would've been around $500 Canadian.
But it did give me an idea for a DIY project that could be as good or better, for fraction of the price.
Doing some research, I discovered that it would be possible to make a solar heater out of cell core ABS pipe. The question was what diameter and what length would produce sufficient surface area and capacity to make it worthwhile. Once I gathered the ABS drain pipe specifications, I entered that data into a spreadsheet where I could evaluate the length, weight, surface and capacity of various diameters of common ABS pipe.
I decided on a 4 inch pipe, 6 feet long, which would give me a capacity of 15 Litres or 4 US gallons.
I started by installing the shutoff valve. I wanted the drain to be as low as possible in the pipe to avoid necessity of having to tilt the system. To ensure the valve retaining nut did not interfere with the pipe once it is glued into the, I positioned the nut away from the wall of the cap using a bolt, which is the same thickness as the wall of the pipe.
For an inflation valve, I was originally going to use a simple rubber Schrader valve. However I opted for a longer valve that is used on aluminum tire rims. This valve uses threaded nuts to secure it in place which I felt was a much better system.
I drilled out a 2” threaded cap and tapped in a radiator valve drain plug that I picked up at the local automotive parts store. This valve will allow me to release pressure from the tank should that be necessary without opening the drain shutoff. Also when open, this will allow a gravity fed system through the drain valve should for some reason I not have access to the air compressor.
To install the filler I first determined the diameter of the fitting and then drilled out the opening on the drill press, using a 2 ⅜” hole saw.
As a final step to improve thermal absorption of solar energy, I painted the surface with flat black paint. First I lightly buffed all the ABS surfaces with steel wool soaked Methol Hydrate. Then applied one coat of spray primer followed by two coats of flat black paint.
At the local outdoor equipment store, I found rooftop canoe pads for just over four dollars apiece. These pads have a slot in them that is meant to go over the gunwales of the canoe and then the solid block would sit on top of your roof with a canoe of upside down. However, the slot is very close to the size and shape of a cross rails on my existing roof rack.
To attach the shower to the support pads are used 1 inch nylon tie down straps.
To test it out we filled it with 30 L of cold water from the Green River, here in Whistler BC, where the water temperature is 4 or 5°C.
Driving around with the truck in mixed sun and cloud all day we now checked the temperature of the heater. After sitting in the shade for about half an hour and it reads 31°. The air temperature is 26°. Inside the tank we see the water temperature is 34°C or 93°F. This is certainly warm enough for a couple of long showers and a very comfortable temperature, considering the alternative is the river.
I found an inexpensive 25 foot, coiled, ⅜”, hose at the local garden centre This would be perfect as it's easily stored and I would not require any larger diameter. We found a multi function spray nozzle for under five dollars that would provide a shower and jet stream capability.
Now, I hook up the compressor to the battery and turn it on. The bursting point of six-inch ABS pipe is well over 100 psi. As such, I determined that 30 psi would provide a safe and ample pressure for our purpose, without any long-term expansion fatigue to the pipe or glued connections.
Overall this project turned out better than the commercial solutions I looked online.
It was an easy and inexpensive project that required minimal tools and just some basic plumbing parts.
I know that is going to come in handy on all our future travels and camping trips.