DIY Solar Hot Water Heater, Http://www.dr-stinky.com/solar.htm

looks like a simple gravity fed system and works well it seems
not sure if you would be able to use it in the built up areas because there is too many regs ( they would lock you up in the UK for sticking this up on your house, and then use real criminals on community service orders to remove it!) but out in the sticks and with no nosey peeps this is a good idea

That's pretty neat!

Wow, imagine if an entire roof was made based on this concept. The potential is huge. In areas where the temp doesn't really drop below freezing it would be practically zero maintenance.

No, cold comes out of the bootom of the heater and thermal siphons into the top hot water tank/ pipe. There are only isolation valves on the panel side. BTW I just bought one of those solar PV panels from Harbor Frieght you've got up on your site. Gonna give it a try on the travel trailer this week. I'll let you all know how it works out.

so, when the water comes in to the electric (or gas) inside the house.. water heater It has a 3 way vauve system ?
Thanks...Rick.

Oops, I meant Farenheit. But I guess you figured that out.

The cold water feed comes in the cold inlet on the top of the W/H were you would normally hook up the cold. The hot feed to the house does the same, it comes out of the hot side of the W/H. I'm putting together a how too plan and diagram to answer all these questions in more detail, stay tuned, or subscribe.

It will freeze unless you shut off the loop and drain it done.

Does this work all year?

And I don't get the routing. Is there cold water going in at the bottom from a T in the cold pipe? And hot water coming in through the top? Where does the hot water come out?

What happens when the ambient temp drops to 20 degrees centigrae?