Black Plastic Pipe Shower
Here is an email describing what looks like a pretty high capacity and very simple solar shower.
I suppose it might even be used in a simple water supply system to supply all the hot water -- day use only.
I used 500 feet of 1/2 inch black pipe loosely coiled up on top of a roof, connected directly to a water tap, and then directly to the hot tap of a shower, which also had a cold water source.
After letting the sun shine on it for about 15 minutes at an ambient temperature of about 60F, I was able to take a looong lazy shower, mixing the cold and hot water, and after I finished, you just waited another 15 minutes and the shower was ready for the next person.
No containers were used. Jut a direct connection to the tap, for cold water, and a direct connection to the black pipe for hot water.
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