Manchester's city pools are opening today and public pools in many area communities — including those in Bedford and Goffstown — opened in the last several days.
So, just how safe are they?
A packed pool can become a soup of germs that can cause stomach cramps, nausea, vomiting and diarrhea that can take weeks to shake off. While testing and disinfecting pools with chlorine are the primary weapons used to beat back the bugs, health agencies and officials also stress that personal behaviors and hygiene play a key role.
The Centers for Disease Control and Prevention track pool-related illnesses in two-year cycles. In 2006, the national total of reported illnesses was 4,167. In 2008, that number jumped to 13,480.
Tim Wilson, coordinator of the state Department of Environmental Services Public Pool and Spa Program, said that while recreational water illness cases have increased, New Hampshire has not seen any major outbreaks.
"In general, it's a small percent of pools overall that have an issue," said Wilson, adding that a larger number of illnesses come from ponds, lakes and the ocean.
New Hampshire's 2009 total of all recreational water illnesses, the most recent figures available, was 318 cases.
The CDC stresses that a significant number of pool-related illnesses go unreported. Wilson agrees that people who come down with a nasty bout of stomach cramps and diarrhea a couple of days after visiting a public pool may never connect the sickness to the swimming.
Bugs and bacteria enter pools on the bodies of people who haven't showered. Swimmers recovering from a case of diarrhea can sicken an entire pool full of people. Dirty feet and toddlers in diapers are among the potential sources of germs that cause illnesses.
To keep people as safe as possible, pool operators test chlorine and ph levels and keep them at an amount high enough to kill contaminants.
"We test every hour on the hour," Goffstown Parks and Recreation Director Rick Wilhemi said, noting: "Every day is different."
This past weekend, Goffstown opened its two pools at Roy and Barnard parks, "Seventy-six days to go," Wilhemi said with a laugh.
Lifeguards at Bedford's public pool test the water every two hours. Nashua Health Officer Heidi Peek said testing increases with large crowds and hot weather.
"Whoever manages the pool tests according to different factors, like bather volume," said Peek. "At the five city-owned pools, it gets done pretty regularly throughout the day."
Keene Parks and Recreation Director Andy Bohannon said state regulations require three tests a day at the city's two public pools; under certain circumstances the staff will test more often.
"If it's crowded or if there has been a lot of rain, we keep a close eye on the water," he said.
When it comes to keeping swimmers safe, most people put their confidence in chlorine.
"Everything is in parts per million," said Wilhemi. "As long as the chlorine is between 1.5 and four, we're good. Nothing can live in chlorine."
Well, almost nothing. Cryptosporidium, better known as crypto, and giardia, two of the most common swimming pool parasites, have protective outer shells that have made them resistant to chlorine. They may die eventually, but it takes more time, which gives the bugs more opportunities to infect swimmers.
And chlorine can cause its own set of problems. When people jump in a pool coated with suntan lotion, perfume and sweat, those substances mix with chlorine and form chloramines.
Chloramines can sting eyes, burn noses, trigger rashes and cause breathing trouble, especially for people with asthma, Peek said. And when chlorine reacts and becomes chloramines, it's no longer doing its job as a disinfectant.
Peek said chloramines tend to burn off in the sunlight and are typically more common with indoor pools. A tell-tale sign that a pool is having troubles with chloramines — a strong smell of chlorine drifting off the water.
"People smell that and they think chlorine is supposed to kill stuff, so the pool must be clean," said Wilson. "That's not the case."
"That's why it's so important for people to shower and pay attention to hygiene," said Peek, who added that the lifeguards at Nashua's pools do a good job of making sure everyone showers before swimming.
"I've heard them say to people heading toward the water, 'Your hair isn't even wet.'" she said.
Bedford Health Agent Gary Pariseau admits enforcing good hygiene is an almost impossible task. There are other signs of problems that are easier to pinpoint, he said.
"You have to be able to see clearly to the bottom," said Pariseau. "If the water is cloudy, the pool closes."
Another red flag: The sides and bottom of a pool should not feel slippery or slimy
Pariseau feels confident in a pool's safety as long as the chlorine and ph levels stay within the set parameters.
Wilson said public pools are required to document chlorine and ph levels whenever they test.
"That's public record and anyone can request to see that information,' he said.
Manchester's pool rules and information remind swimmers about those logs and records and encourage swimmer to ask for information. Manchester's four pools and Crystal Lake are scheduled to open today, however some hours are restricted to city residents only.