Casing

• The first thing to decide is what you will use for your solar water heating panel casing. If you are handy with sheet metal work, a sheet metal case is lighter and easier to handle than a wood cased solar water heating panel. Wood, however, is easier to work with and assemble. Simple plywood should suffice. Take the overall size and weight of the panel into account as you design your casing. With water in the pipes, the weight of the panel will increase and you may want to add some bracing to your panel casing.
  
  

Lining

• Dark lining and dark paint on the pipe will help absorb the sun's light and transfer it to the water flowing through the pipes. Although there are a number of commercial products available, flat black paint should work very well. The problem with some flat black paints is that they may fade under the sun. The paint may need to be re-applied every year or two. For more efficient heating, you may want to add a layer of insulation to the back and sides of the casing and paint the surface of the insulation black. Be sure to paint your pipes black also.
  
  

Pipes

• Although high heat PVC pipes will probably work, using copper pipes will provide more efficient heat transfer. Run the pipes back and forth in your casing. Remember, the longer your water stays in the solar water heating panel, the more heat energy is transferred to the water. Copper pipes also have the advantage of not corroding like other metal pipes.
  
  

Glazing

• For thermal efficiency, you will want to enclose the entire top of the panel in glass. This will trap heat via the greenhouse principle and increase the efficiency of your solar water heating panel. In some cases, double paned glass may provide for additional efficiency, especially in colder climates where heat from the panel may be quickly lost into the cold air.
  
  

Very Cold Climates

• In very cold climates, be sure you insulate the feed pipes. If they freeze, they can burst and can disable your entire system. In some cases, it may be a good idea to install a system that uses an indirect heat transfer system passing through your existing hot water heater. In this type of system, the water can be kept moving, transferring heat to the hot water heater during the day and using the hot water heater to prevent freezing of the solar system at night. Although on very cold evenings, this may use gas or electricity at night, the temperature of the hot water heater can be set very low to minimize energy impact. The savings of using primarily solar-heated water should more than offset the night time energy costs.