CARY — If you thought flappers are just party-time girls from the Roaring Twenties, guess again. They are also plumbing devices, and the town of Cary wants its residents to have the most up-to-date versions, called early closure flapper valves.

Amusing it may sound, but water conservation experts find it a very serious matter. Installation of such devices could save significant amounts of water, and reduce homeowners' monthly water bills.

These early closure flapper valves replace ordinary valves in bathroom toilet tanks. By closing faster than the standard valves most homes now have, less water is used in each flush.

The new devices ensure than no more than two gallons of water leaves the storage tank to flush the bowl. Standard toilets use 3, 5 or 7 gallons to flush a bowl.

To spur residents to switch flapper valves, the town of Cary will reimburse residents for half the cost of the $7 price tag. The new flappers will work only on older toilets. Since 1994, new homes may have only low-flow toilets, as required by the National Energy Policy Act.

Given Cary's enormous growth, and more expected, water is a serious issue. The city's population is expected to be 100,000 by the year 2000. Frequently in summer, residents are told to reduce their water consumption. Town officials are waiting for state approval to draw an additional 40 million gallons of water a day from Jordan Lake.

Still, the flapper could also play a part in cutting water use. Greensboro initiated a similar program, and now their water conservation staff estimates that the flappers save more than 100,000 gallons for the city.