Dear Jim: My son’s sixth-grade teacher said we can save half our water heating energy by building a simple solar water heater. Now my son is bugging me to do it. Is the teacher correct and how can we build one cheaply? – Ken N.

Dear Ken: It looks like you will be building a solar water heater one of these weekends instead of golfing because your son’s teacher is correct. Luckily, there are many effective designs that are inexpensive to build. If you are not handy with tools, kits or preassembled ones are also available.

During the summer, with the intense sun and lower hot-water needs, the simplest batch-type solar water heater can contribute up to 50 percent of your hot water. It will produce about 25 percent during fall and spring and you may choose to shut the water valve to it over winter to avoid freezing.

In addition to a $100 annual energy savings, a simple solar water heater increases the hot water output from your existing water heater. With the water entering your house already warmed by the sun, the first-hour rating (how fast it heats incoming water) of your water heater is greater.

The easiest type of solar water heater to build and install is a batch solar water heater. As mentioned above, it is usually connected to your water heater as a preheater for the incoming cold water. Without having to be concerned about the actual water temperature, installation is simple.

The simplest batch water heater is basically a large black water tank that is placed in a sunny location. You can purchase a 50-gallon water tank, but first check with a local plumber for a discarded water heater that did not leak. Strip off the metal jacket and insulation and paint the tank black. A water heater tank will already have inlet and outlet pipes and a drain.

For more efficiency and hot water output, mount the water tank in an insulated box with a clear cover. Make the box with inexpensive wall studs and plywood and line the inside with fiberglass wall insulation. Cover the top with a single layer of clear acrylic plastic. You can find large clear plastic sheets at most home center stores.

If your son wants to impress his classmates, make a hinged insulated cover for the clear plastic top. When you close this at night, the water in the solar batch tank will stay warmer through morning and help out for morning showers. In cold climates, add a second clear layer during the winter.

It is best to locate the solar water heater against your house on the south side. Add two tees in the cold water line leading to your water heater and connect them to the batch solar tank. Include a valve after each tee and one between them. These allow you to bypass the batch heater when you wish.

Write for (instantly download – www.dulley.com) Update Bulletin No. 695 – do-it-yourself instructions, diagrams, materials list, plumbing schematic for several designs of batch solar water heaters, and a list of ready-to-install solar water kits. Include $3 and a business-size SASE, and send to James Dulley, 6906 Royalgreen Drive, Cincinnati, OH 45244.