The nearly 1,000 swimming pools in Salt Lake County ring out with laughter all summer long as swimmers splash and play away hot days in the cool waters of public, hotel and condo swimming pools. Similar scenes play out in virtually every community statewide.

But it's likely that some of the revelers are doing other things, as well, a fact which keeps health inspectors and pool operators vigilant.

Recreational water illnesses, shorthanded to RWI, are on the rise nationwide, according to Salt Lake Valley Health Department officials. In a single outbreak, 3,800 swimmers in New York were affected and the pool was closed for almost a year. RWIs are caused by fecal matter in the pool.

Tuesday, health department and pool officials gathered at Cottonwood Heights Community Recreation Center's busy outdoor pool, which sees as many as 2,000 swimmers a day, to talk about "healthy swimming behaviors" to prevent illness caused by pool contamination.

Yes, pools are chlorinated, the experts say, and that greatly reduces the risk of waterborne illness. But it's not an instant fix. Germs respond to chlorine at their own pace, from the mere minute it takes proper levels of chlorine to kill E. coli to the many hours and even days it takes to destroy cryptosporidium (the cause of the New York outbreak), depending on the concentration of chlorine.

The waste in the water can also spread giardia, shigella and hepatitis A. Contamination usually results in diarrhea, but it can also cause skin rashes, ear infections and respiratory infections.

Local health departments send inspectors out monthly to sample pH and chlorine levels and check for RWI-causing germs. The pH level is important to maintain the chlorine level. Regulations require staff at pools like this one to sample water every four hours.

But the sampling probably does less to keep the water safe and the RWIs at bay than simple steps the public can take, says Teresa Gray, an environmental health supervisor for the Salt Lake Valley Health Department.

"Someone who has diarrhea or is sick has no business being in a pool," she says.

No fecal matter belongs in the pool, but diarrhea is particularly problematic because it travels faster, farther, is harder to contain and can contaminate more water at once.

Gray offers simple tips. Shower before swimming and use soap on the kids. Parents need to change babies' diapers away from the pool and deck area, preferably in the restroom. They need to ask their kids whether they need to go to the bathroom before ever getting in the pool and about every hour after that. "When a kid says he has to go, it's probably too late," Gray says.