A decade ago, clinics and hospitals in western New York were flooded with patients (mostly kids) complaining of severe stomach pains, vomiting and diarrhea. More than 2,000 people fell ill. The source of the mysterious outbreak turned out to be a recently opened “splash park” in a nearby state park.

Investigators paid a visit to the splash park and discovered a parasite called Cryptosporidium (also known as “Crypto”) in the water tank. The main cause of travelers’ diarrhea, the parasite lodges in the intestines and produces eggs that later hatch and sicken the unlucky carrier. Nine years later, the state settled a lawsuit with the victims for $5 million.

Today’s splash parks, also known as spray parks and splash pads, may — or may not — be any cleaner. 

Smaller kids love these play areas, which let them get wet on a hot day and splash in the water that shoots up from spouts in the ground. And parents may assume that since there’s no drowning risk, they’re safe. But the risk of getting sick from bacteria may actually be higher than the risk in a swimming pool.

Splash parks or cesspools?

The water in these fountains is often re-circulated through an underground reservoir, where it is filtered, chlorinated and then pumped back out. In theory, chlorinated water is clean water. But here’s the problem: While chlorine kills most germs, it doesn’t work instantly. Some germs are killed within minutes, while others — like Cryptosporidium — are resistant to chlorine and can take days to be killed off.

What’s more, splash parks use a smaller volume of water per user than swimming pools, which can increase the risk for the spread of waterborne illness. Just one child with diarrhea can easily contaminate a splash park, turning the play area into an outdoor cesspool.

If a child swallows just a small amount of water, she can get sick — and swallowing or gargling with the fountain water is something some kids love to do. In a 2010 study of kids’ behavior in Idaho splash parks, researchers observed that nearly one in four children put their open mouths up to the water.

“Splash parks are very fun places and great sources of recreation in summer,” says Randall Nett, MD, MPH, a medical officer with the Centers for Disease Control and Prevention and the principal investigator who led the study. “But because they are so popular, we need to ensure that we make them safe for our most vulnerable children.”

Related: Play It Safe at the Water Park

Dirty play

Kids drinking the fountain water is one problem. But the researchers witnessed some more troubling behavior: Nearly half of the children and toddlers (many in diapers) pushed their backsides against the waterspouts, which could spray fecal matter from the child’s bottom back into the water supply.

Since many children using splash park aren’t potty trained, dirty diapers are a big concern. Some parks require swim diapers with plastic covers, but not all public parks have such rules or anyone to enforce them. In Nett’s study of Idaho splash parks, 38 percent of the children in diapers were wearing only disposable diapers (which, as parents know, tend to leak).

Crypto infections from splash parks and pools jumped from about 3,400 cases to 10,500 in recent years. Giardia, Shigella, norovirus and E. coli are other germs that have caused outbreaks at splash parks.

Tips for safer splashing

Before you let your child use a splash park, you might want to do some research on how the water is sanitized.

Parks should maintain proper chlorine levels and regularly check them. But experts also recommend an additional layer of protection, like UV light or an ozone disinfection systems. “Although [UV light] is more expensive, it does a much better job against parasites like Cryptosporidium and giardia,” Nett says. After the Crypto outbreak in New York, the state began requiring the use of UV light in addition to chlorine and filtration.

Splash parks nationwide still aren’t regulated in the same way pools are. In fact, most require no construction review, supervision or routine inspections.

Since many states don’t require routine health inspections, it’s difficult to know if the splash park you visit is clean. Start by asking if the park follows the 2014 Model Aquatic Health Code’s guidelines, which the CDC developed in response to outbreaks of illness in pools and splash parks.

Although they are voluntary, these guidelines include recommendations on chlorine levels, UV light disinfection, filtration and splash park design.

You can also help protect your kids and others by following these tips:

  • Bathe your child thoroughly (especially the rear end) with soap and water before going to the splash park.
  • Don't allow your children in the splash park if they have diarrhea.
  • Discourage risky behavior among children — in particular, don’t let them stick their backsides or mouth near the waterspouts or swallow the water.
  • Change diapers in a bathroom or a diaper-changing area away from the splash park and wash your hands with soap afterward.
  • Do not picnic or drink in or around the splash park.
  • Take kids on bathroom breaks or check their diapers often.

Related: Test Your Summer Sun Smarts

Kids will happily jump around in the spray for hours, so don't forget to watch out for sunburn and heat exhaustion. But most of all, take into consideration whether your wee ones can resist gargling in those inviting sprays of water. Older children may be able to resist the temptation, but for little guys, that’s a tall order. For them, playing with a hose in the backyard might be safer — and just as fun.

Related: Inflatable Pools: Small Doesn't Mean Safe

Mary Purcell is a freelance writer and health researcher in Piedmont, Calif., with expertise in policy analysis. She has a master's degree in Latin American studies from Georgetown University.