How to Make Solar Hot Water

Building a solar hot water heater can immediately reduce energy costs and can be utilized in any climate. "On average, if you install a solar water heater, your water heating bills should drop 50%--80%" (References 1). However, it is important to note that it is necessary to have a backup hot water system for those cloudy days or periods of higher use.

Things You'll Need

• Water heater tank (not currently in use)
• Plywood box big enough to hold the tank
• 2 sheets of clear plastic or glass
• Plumbing fittings that will connecting the solar heater to your traditional hot water heater
• 6 bypass valves
• Insulation
• Black paint
• Paint brush
• Power drill with wood bit big enough for pipe fittings
• Silicone caulk with caulk gun

Instructions

1. Find a south facing slope, where sunlight will hit more than other areas. Preferably, you will also want the solar hot water heater to be close to the traditional water heater, thus eliminating some of the heat loss from warm water running through a labyrinthian network of pipes. This south-facing slope will be the home of your new solar hot water heater. Placement and orientation can be the "single most important" factors to consider when constructing a solar water heater (References 3).

2. Clean your extra hot water tank with a wire brush and paint it black. Prepare the tank by making sure that you have the correct fittings to run the water from the tank to the rest of the water heating system. Ensure that if you are placing the solar water heater at an angle for maximum coverage by the sun, and that the cold water inlet is still at the bottom of the tank. (Resources 3)

3. Construct the box. The size of the box should allow for the glass front to cover 1 square foot for every 2 to 2.5 gallons of water. This will ensure that you will have a large enough size for adequate solar gain. A standard patio door replacement glass (34 inches X 76 inches) is ideal for a 40 gal. water heater (Resources 3). Obviously, the box should also be big enough to fit the tank.

4. Place the tank into the plywood box and insulate the plywood box further by utilizing double-paned windows or multiple layers of close so that the trapped air will add as an extra measure of insulation. Using silicone to caulk the plywood box will also help seal-in the heat as well as keep unwanted moisture from the outside environment from getting inside. Finish preparing the box by drilling holes for pipes and installing insulation.

5. Connect solar water heater to the traditional water heater already being utilized in your home. Place two bypass valves leading from the cold water supply to the solar water heater and the traditional water heater so that you can regulate which heating system the cold water flows to (References 2). Run piping from the hot water outlet on the solar water heater to the cold water inlet on your traditional heater so that the hot water is running into your existing water heater already hot.

Tips & Warnings

• The shorter the plumbing between the solar water system and the traditional water heater, the lesser the chance of the water freezing during the colder months. Insulating the pipes will help reduce heat loss in the transfer of warm water from the solar system to the traditional water heater. A little more research and planning can help place the remaining bypass valves for the piping. You will want to consider how to obtain the versatility to have cold water going into both heating systems, being able to go on 100% solar, or not doing any solar at all.

• Putting a full water tank on top of a roof may cause serious structural damage to your roof as it will weigh well over 300 pounds.

References

• The Economics of a Solar Water Heater
• Solar Water Heaters
• Mother Earth News

Resources

• The Renewable Resource Data Center
• Solar Radiation Data Manual
• Epsea