Generally, pool water needs to be replaced once every five to seven years. This should be done during mild weather so that your pool surface is not at risk from strong sunlight and heat. Your pool maintenance company can recommend when it is time to drain your pool.

Pools that are unattended, without chemicals, circulation and cleaning, don't last long. Within weeks, they become green, and within months, they become home to frogs and mosquitoes.

And if you're going to a community pool, there should be regulations and inspections to make sure you're swimming in safe waters. To be considered safe, the chlorine concentration in a pool should be high enough to control any potential pathogens in the water, Tetro says. This is usually about 1 part per million.