Thank you for answering my more than a year old question about a spiral of pipe. Frankly, I had forgotten about it and shleved the idea. But now I may go ahead with it. The idea is to use PEX high dtemperature plastic pipe, painted black and coiled up in the sun, as a water heater for my RV. I got the idea when I nearly burned my hand with water from a garden hose left in the sun. I reasoned that if the water was that hot from a light colored garden hose, how much hotter would it be if the "hose" were black (dark green has been shown to be better) and "under glass" - but the question was, how much "hose" (pipe) could I fit on the roof and would there be enough water to be useful? Your answer shows that the idea is feasable and probably affordable. Thank you- gabbyjim, Idaho Falls, ID, USA