As cities open their swimming pools for the summer, Philadelphia thinks it can get more aquatic fun for its buck from water-sloshing pipes.

Philadelphia is replacing one of its older pools with a "sprayground." If the experiment goes well, the city may do the same with a few more pools that are reaching the end of their 30-year lifespan. The cost of filling in a pool and replacing it with a sprayground is about $400,000 less than building a new pool. Spraygrounds are also cheaper to operate because no lifeguards are needed.

The shift from pools to spraygrounds is something of a national trend. Kids love them, much the way they used to enjoy uncorking fire hydrants on hot summer days. Recreation centers find that spraygrounds can serve more people--and make more money--than a pool. Recreation Management magazine recently declared that "the old rectangular community pool is a vestige of a bygone era."

Critics worry that splashing will overtake swimming at rec centers-- at a loss of water-survival skills. "A sprayground is not a substitute for a regular swimming pool," says John Spannuth, president of the United States Water Fitness Association. "It doesn't eliminate the responsibility of cities to teach every child in the community how to swim."

Philadelphia hasn't forgotten that, says Carlton Williams, who was a deputy commissioner with the city parks department when the sprayground decision was made. The city still has 79 pools citywide, he notes, and the neighborhood that is getting the first sprayground has another pool only six blocks away.