Building a PVC pipe solar hot water heater can reduce or eliminate the need to use "grid" power to heat water for the home. By using PVC pipe encased in a heat-building box, then installing this box in a location that receives ample sunlight, the water is heated and pumped into the home using thermal energy. Installing several of these heat boxes will provide an abundance of hot water, and can be built and installed by an average backyard engineer in about three hours.
Build the heater box. Using the plywood as a base, nail four 2x4 boards around the edge of the plywood to make a shallow box. Screws can be used for added stability.
Drill holes large enough for the PVC pipe to fit into, one on the top left edge, one on the lower right edge. They can be on either edge of their corner, but they must be placed on opposite corners.
Attach a layer of plastic thermal film to the plywood and up the edges of the 2x4's, leaving spaces for the drilled holes.
Assemble the PVC pipe inside the box, in a radiator pattern. Run one pipe from the hole down the inside edge of the box. Then, using a pipe adapter and glue, take the pipe to a 90-degree angle. Add a small section of pipe, then another 90-degree pipe adapter, so that the pipe makes a "U" shape. Run a length of pipe to the opposite edge of the box and repeat the "U" shape so that the pipe runs the entire length of the box in a series of bends. This will maximize the exposure of water inside the box to the sunlight provided. The last section of pipe should meet the second drilled hole at the lower right of the box.
Paint all pipes and the inside of the box with low-gloss black paint. This can either be standard acrylic spray paint or brushed-on lacquer paint. The objective is to make the inside of the box and all interior pipes a dark black color.
Cut and mount the plexiglass cover to the top of the box, sealing it. The pipe glue can be used, or small holes can be drilled into it and nails or screws can secure it.
Mount the box in a high-sunlight environment. Most homeowners opt to place it on the roof, as it is a flat, angled surface that gets a lot of direct light exposure. The box can be mounted to metal "L" shaped connectors, screwed into both the box and the mounting surface.
Attach the home's hot water supply to the pipes in the box. The upper left pipe on the box is the input, and the lower right hole is the output. As the cold water is pumped into the box, sunlight will be absorbed into the black surfaces, heating the pipes. The water will exit the box and enter the house at a substantially higher temperature.