How to Convert an Old Water Heater to a Solar Water Heater

Billions of photons stream from the Sun to the Earth. When photons strike the Earth’s surface atoms begin moving faster. The increased speed generates heat and is the theory behind thermal conduction. This is what solar power is based upon. Solar water heaters use no moving parts, just a heat collector box.

This passive method can heat water up to 150 degrees Fahrenheit.

The Water Tank

  1. Locate the water heater. Look in local junk yards or at homes being remodeled. Ask about pricing and choose a water heater in good condition for your price range.

  2. Remove the outer enclosure. Remove the insulation. Remove the pipe fittings. You want only the metal tank that makes up the core of the heater. Discard and recycle the parts you removed according to local ordinances.

  3. Fill the tank with water. Check for leaks. Empty the tank and rinse out any sediments.

  4. Sand the tank exterior thoroughly. Spray the exterior with the black paint. Use multiple coats. The paint protects the metal from moisture while aiding the heat absorption.

  5. Screw the water supply fittings to the old connections on top of the tank. You need one for cold water to flow from the house to the tank and the other to deliver hot water from the tank to the house. Install the drain spigot to one of the holes on the side of the tank. Install the pressure release valve near the fitting for the water supply. Plug the remaining unused holes in the tank.

Collector Box

  1. Measure and cut the lumber to accommodate the size of the tank. Allow for a few inches clearance around the entire tank.

  2. Build the collector box. Build two squares from the shorter lumber for the top and bottom. Use the longer lumber to make the sides.

  3. Measure and cut three sections of plywood for the sides of the box. Measure and cut a square piece of plywood to be the base of the box.

  4. Cut three lengths of 2-by-4-inch lumber to match the curve of the tank base. These become the supports. Attach the support lumber to the base sheet of plywood.

  5. Stand the box up. Set the base sheet upside down over the top of the box. The supports should be facing the floor. Attach the base to the box with screws. Flip the box upright and set in place where the heater is going.

The Walls

  1. Lower the water heater into the box. Rest the base on the supports squarely.

  2. Measure and cut three sections of insulation 4 inches smaller than the plywood sheets on all sides. Lay insulation onto each sheet with the reflective side facing outward. Center the insulation and staple it into place.

  3. Mount each of the three insulated sheets to the box to form the walls. Set the walls with the insulation facing the tank. Keep the south face wall open. The insulation should fit between the corners of the box. Attach each wall to the box with screws.

  4. Attach the window clips to the inside edge of the open box side. Slide the appropriate glass piece into place from the top. Mount the smaller glass piece onto the top of the box. These will collect the sunlight.

  5. Prime and paint all wood surfaces. This helps maintain the box durability against the elements. Caulk all the seams to retain heat and keep moisture out.

Attaching Heater

  1. Attach the water lines from the house to the heater. Attach the overflow hose to the pressure release valve. Run the overflow hose out the bottom of the box.

  2. Turn on the water. Fill the tank and test the lines.

  3. Wait 24 hours for the water to heat up. This gives enough time for the heater to begin working.