Chandler will become the second Valley city to filter all its public pools with ultraviolet light in a battle to kill bugs that can cause severe illness.
The new filter's primary target is cryptosporidium, a parasite that causes diarrhea, but it will also kill giardia, E. coli and other chlorine-resistant bugs.
Tempe has added the UV filtration as well, following cryptosporidium outbreaks across the nation that have sickened hundreds of swimmers at a time. The bug triggered pools across the Valley to close in 2008 after it was discovered in a Phoenix public pool, but testing at other pools generally failed to find the parasite.
Cities have generally resisted the UV systems because of the cost. This month, Chandler approved about $693,000 to install the systems in its six public pools. They'll be in place when the pools reopen in the spring, said Sheri Passey, aquatics superintendent.
Chandler tested its pools after the 2008 outbreak but didn't find any crypto. But the city wanted the filters because the parasite lingers so long and testing for it requires lengthy waits to get results.
"Cypto can live up to 11 hours and sometimes even weeks at a time in a well-maintained, chlorine-treated facility," Passey said. "It's becoming more and more resistant to chlorine and the UV is really the only thing that ... kills it."
The filter could reduce the amount of chlorine used - and also reduce the sometimes overpowering chlorine smell in pools, Passey said.
Tempe installed a UV filter at the splash pad at Tempe Beach Park at the time of the 2008 outbreak, though the system had been ordered well before that, said David Bucher, a Tempe recreation administrator.
The filters are working at the Kiwanis Wave Pool, and the Escalante Pool will have a system hooked up within weeks.
"I would not build a new facility today without UV," Bucher said.
Mesa has UV filters at its two wade pools, but not in its public pools, said Aimee Manis, the city's aquatics coordinator.
Gilbert does not have UV filters and is not considering them at this time, town spokeswoman Beth Lucas said.
Cyrpto is spread through fecal matter. Once it is found in a pool, it can be eliminated by hpyerchlorinating the water. That requires closing the pool for days.
Pool operators ask swimmers to reduce the odds of spreading crypto or other bugs by showering before entering a pool. Also, swimmers should stay out of the pools if they've had diarrhea within two weeks, and parents are asked to take kids on frequent bathroom breaks.