Q - I think it might cut my utility bills to add insulation to my old water heater tank. I have some fiberglass wall insulation left over from another job. Can I use it on my water heater tank? O. C.

A - If you have an old water heater, chances are there is inadequate insulation in the tank walls. A poorly-insulated water heater tank can lose up to 30 percent of the water's heat to the surrounding air. This can total to several hundred dollars wasted over the life of a water heater.One quick test to determine if your water heater could use additional tank insulation is to place the back of your hand against the upper side of the tank. If it feels warm, then it is losing too much heat.

If you have some old wall insulation, you can save the cost of purchasing a special water heater insulation jacket. Insulation with a foil or kraft paper backing is easiest and cleanest to use.

With an electric water heater, it is a very simple job to add tank insulation. Cut the insulation into lengths to fit horizontally around the circumference of the tank.

With the kraft paper on the outside, staple the ends of the paper together. You will need several lengths to cover the entire tank. Cut a circular piece of insulation for the top. Slit it so it fits around the inlet and outlet water pipes.

Insulating a gas water heater is a little trickier. You must be careful not to block the combustion air inlet and the draft diverter at the top of the tank around the flue.

You can use bent coat hangers to form long vertical hooks that hold the pieces of insulation in place. Using coat hangers, make a support circle around the flue pipe a couple of inches smaller in diameter than the tank. This rests on the top of the tank to support the hooks and insulation.

Make four hooks from coat hangers that, when bent around the support circle, hang down about 14 inches. Make another set of four 14-inch-long hooks and hang them from the first set. Continue this until you are about one foot from the floor. The last set of hooks will be shorter.

Wrap a length of insulation around the tank and hooks and staple the paper backing together. This should rest in the top set of hooks. Continue down attaching lengths of insulation until the entire tank is covered.

You can write to me for UTILITY BILLS UPDATE No. 055 showing do-it-yourself instructions and diagrams for insulating a water heater tank and a list of tips for reducing your water heating costs. Write to James Dulley, The Deseret News, 6906 Royal Green Dr., Cincinnati, Ohio 45244. Please include $1.00 and a self-addressed envelope.

Q - I have a heat pump. My house always seems to stay warm, but when I put my hand by the warm air register, it feels chilly. How can it keep my house warm? D. L.

A - The heated air output from your heat pump is cooler than that from an electric, gas, or oil furnace. Its temperature, as it reaches your hand, is lower than your body temperature. The slightly cooler air feels even cooler because of the wind chill effect.

Since you keep your house in the 68 to 70 degree range, the air output is hot enough to keep it warm. Heat pumps tend to run longer and move more air than other furnaces because the air coming out isn't as hot.