Solar Hot Water
DIY Project
An extra susbstack this week…on a totaly different topic. I know, my solar water heater looks a little like Israel’s Iron Dome rocket defense system, but it’s not quite that sophisticated…
A fun project - Hot water plumbed on a loop so that the incoming household water is diverted to the solar tank first before going into the regular hot water tank. The loop can be shut off, bypassed and drained during the winter freezing months. This is sometimes called a “breadbox”. It’s a simple passive solar water heater with no moving parts to maintain. I built one 23 years ago, leaning against the house, and it worked great until I re-roofed with metal and the snow slid off and broke the glass front. So I’m rebuilding the box and moving it away from the house. I was able to reuse the tank and some other materials.
The loop
I ran the piping for the loop through the floor, under the house, and out through one of the foundation vents to the solar tank. The shut-off valves have red handles.
Used tank
It started with finding an electric hot water tank that had been switched out for a gas tank. The electric tank was still good, but I got it very cheaply. The only thing I cared about was being assured that it wasn’t a leaker. I stripped the shell and the insulation off the tank and painted it flat black.
Used window
Next I shopped for a 2nd hand window, which I also got very cheaply. I wanted to get the window before building the box, because I needed to know the dimensions of the window in order to build the box to the right size. This particular window is 54”X72”.
“blueprint”
Next I sketched out some plans. A 50 gal tank of water weighs over 400 lbs, so sufficient support is needed. I mixed a little concrete to make enough of a base to keep the wood off the ground, and a 2nd one for the framed brace that would hold the box up at a 45 degree angle.
Framing, boxing in, and insulating
I made the frame and the brace, covered the box with plywood and insulated the sides, top, bottom, and back with 1” ins. board. I cut an access panel in the back to be able to get at the plumbing.
I made a parabolic reflector out of Masonite and painted it white, to get maximum sun directed right at the tank. I cut a hole in the back to allow the tank drain valve stick through to the outside, so I could drain the tank in the winter. I also cut holes in the back for the two water lines.
Plumbing
I placed the tank in the box, and plumbed it in using CPVC pipe. The pipe runs to the house and back to the standard electric tank. The solar tank will just act as a pre-warmer most days, but it can get up to 120 degrees on a warm sunny day.
I put additional drain valves in a 5 gal bucket so I could drain the pipes as well as the tank. I’m insulating the pipes where they’re exposed, and also the hot line where it goes under the house. (picture after ditch partially filled in)
How to get the most out of it
Just use hot water in the afternoon, after the solar tank has had time to reach max temp. That means showers, laundry, dishes. Now all you have to do is train your wife to that schedule. LOL good luck
I'm sending this article to my brother-in-law that builds houses in Mexico with Yugo. Most of them don't have electricity or running water, but occasional ones do. He's a mechanical engineer and would probably like to try building one of these.