Q - I am concerned about the purity of our water for my children's health, and I plan to get a water purifier. Are some better for removing cancer-causing chemicals, and are they expensive to operate? H.K.

A - You should be concerned about the quality of your drinking water. There can be many harmful and cancer-causing chemicals in your drinking water. Even the chlorine added to water to kill organisms can react with other chemicals to produce cancer-causing compounds.Your own plumbing system can introduce lead into your water. Unless you house is very new, the plumber probably used lead-based solder. When water rests in the pipes for several hours, lead dissolves in your drinking water. Lead is very hazardous to adults and especially to children.

There are three common types of water purifiers for home use. The effectiveness and cost to operate each varies. Before selecting one, you should have your water tested to determine which harmful chemicals and organisms are present.

You can send a small water sample to labs for testing and request a variety of different tests. At the very least, you should have an inexpensive test done for the lead content in your water.

Activated carbon (charcoal) filters are effective for removing organic compounds, pesticides, benzene, and trichloroethylene. They are not as effective for removing bacteria or heavy metals such as lead. The only cost to operate a carbon filter is replacing the cartridges.

A reverse osmosis (RO) system works by slowly forcing water through a special membrane. It is effective for removing most contaminants, some bacteria and often includes a carbon filter cartridge.

RO systems sized for home use produce water at a slow rate, about one gallon of water in four to six hours. This process also uses a lot of water. To produce one gallon of purified water, about six gallons of wastewater go down the drain. This is a drawback that can be expensive in water-shortage areas.

Distillation is very effective for removing most contaminants, including the lead from your plumbing system. Since the water is first boiled and then condensed in the distillation process, harmful bacteria are killed. Most systems filter the distilled water through a carbon filter, too.

The only cost to operate a small home-use distiller is for the electricity to boil the water. At an electric rate of 8 cents per kilowatt-hour, each gallon costs about 25 cents. In the winter, the heat given off helps heat your house, so the net cost is actually less.

You can write to me for UTILITY BILLS UPDATE No. 371 listing which water purification systems are most effective for removing which contaminants and a list water testing labs and the costs of various tests available. Write to James Dulley, The Deseret News, 6906 Royal Green Dr., Cincinnati, OH 45244. Please include $1 and a self-addressed envelope.

Q - I have lights recessed in my bathroom ceiling, and I can feel air blowing out from them. What can I do to stop the air leakage? G.E.

A - Recessed lights under an attic can allow air to leak into your house.

Since the recessed light fixture canister gets hot, insulation and other materials must not touch it. You should consider removing the recessed lights and installing track lights. You can cover the two holes in the ceiling with a piece of finished wood and attach your track lights to it.