The state of Florida has had a whole lot of rooftop solar water heaters for decades. These are basically just a horizontal tank with a solar water heater panel attached. You mount it with the tank upslope of the panel, and it doesn't require pumps or even electricity. It's not quite as sunny here, so that's why I am using a 250 gallon heat storage tank. And I have a bunch of IBCs my wife used to store rain water. I also have some old sliding glass doors, so I just needed a sheet of plywood, a sheet of insulation, and some plumbing to hook it up.

A lot of DIYers build these systems, but they put the panel above the tank. So they have to use pumps to keep water in the panel or use copper tubing so the panel pipes don't melt. Then they need a PV panel to run the pump if the grid power fails. Thermosyphon is much more reliable for keeping the plumbing a safe temperature and costs nothing to run being inherently solar-powered.

BTW, the thread should be "Solar Hot Water System" but I couldn't figure out how to fix that without a lot of hassle.

Educating anyone benefits everyone.