How clean is your pool? Most operators feel confident when asked that question, but local inspections have revealed some alarmingly unsafe pools, most often in places such as apartment complexes and hotels.

In Los Angeles County, Calif., Los Angeles Times staffers surveyed more than 16,000 pools inspected by the county health department. Pools were in all types of locations apartments, schools, health clubs and hotels and the Times found 10 percent had been closed by inspectors at least once in the past 3 1/2 years.

In visits to six of the eight pools with the most violations, Times staffers discovered three with ?murky or green water.?

Kern County, Calif., inspection records show similar results. Since May 2007, county officials have closed 15 percent of the approximately 875 pools (most at apartments or homeowners associations) they inspected.

?We like to be as proactive as we can,? said Guy Shaw, Kern County chief environmental health specialist. He noted that violations range from poor water quality to problems with ground fault circuit interrupters. Shaw added that he sees problems in public pools, but most are well- maintained.

Susan LaBay, environmental health training officer at the Southern Nevada Health District, agreed: ?Usually [public pools] are fairly good.?

The SNHD inspects nearly 5,000 Las Vegas County pools every year.

?In the casino areas, we rarely get a closure; they?re very proactive. Most problems happen in apartment or HOA pools,? Labay said. She noted the biggest violations are missing, broken or noncompliant barriers, or noncompliant levels of disinfectant.

An investigation in Calgary, Alberta, Canada, found problems at public pools. Water samples from seven of 16 city-owned outdoor pools contained the bacteria coliform, which can be found in fecal matter and is commonly used to determine the sanitary quality of food or water.