check out this site and magazine, in one of the last articles they had one on solar hot water,
good magazine on renewable energy and the how to to do it.
I think you can down load the current issue, plus they have some guides you can down load.
http://www.homepower.com/
there beginners guide to solar hot water,
http://www.homepower.com/files/beginner/SolarHotWaterBasics.pdf
current article on sizing a solar hot water system,
http://www.homepower.com/files/featured/SizingSolarHotWaterSystems.pdf
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depending on how simple you want to go, get a clean 55 gallon steel drum, preferable one that has been plastic coated for corrosion resistance, paint the out side black, build a mount or stand to put it on, and fill with water in the morning and at night you will have hot water, and let gravity feed it, (by turning the drum up side down you can use the existing bung holes to attach to, you will to put a hole in the "bottom" of the drum that is now on top to fill it). you will need a good platform to set the drum on as water weighs nearly 8 pounds per gallon.
need more hot water put two drums in,
No they don't work well in the winter.
Many of this type of solar hot water heater was used as a shower houses, in the military, and on farms, and camp grounds, before running water and electricity. and propane services.
A shower house with one still sits on my father in laws farm. Made with 4 posts and some lumber for sides with a pallet type floor, and a deck for the drum to set on, the shower head has a valve on it, coming directly out of the drum.
(my guess is this type of heater would not go over very well with inspectors).
do some Google searches on solar hot water there is a lot of information on some simple system,
http://www.google.com/search?source...GGIH:en&q=drum+hot+solar+water+heater++shower
http://www.google.com/search?num=50...q=+hot+solar+water+heater++shower&btnG=Search