A car radiator makes a sturdy, cheap, solar heater. These simple steps will produce a basic design suitable for use as solar water pre-heater.
What materials and tools will I need?
This basic design requires one car radiator, flushed, pressurized to check for leaks and repaired, if necessary. Two rubber radiator hoses and two hose clamps used to attach the radiator in series with the water supply. Finally, black spray paint completes the list of materials. Tools required include a straight screwdriver and a rubber mallet.
What do I do next?
Use the rubber mallet to tamp all the fins flush with the surface on both sides of the radiator. Tamping all the fins increases heating efficiency, in this application. Next, paint both sides of the radiator thoroughly; use at least two coats of black spray paint.
Where do I put it?
Attach the radiator in series before the water heater. Find a location on the south side of the house in direct sunlight.
Is that all there is to it?
Depending on the climate, a housing built around the unit will increase its efficiency. Make sure to use tempered glass on the top. Tempered glass will endure the heat.