If the community pool closes for the day and the kids ask why, Goose Creek mother Michelle Combahee tells them straight up: It has to get cleaned.

The day her younger daughter asked why, Combahee told her that, too. 

"Ewwwwww" was the reply.

The Memorial Day weekend is underway, the unofficial click of the burners on another very hot Southern summer. Everyone who doesn't go to the beach wants to go to the pool. There, beside the dazzling lapping waters and the fresh scent of chlorine, few stop to wonder whether they should jump in.

But the water's not always pure.

One of every four adults admits to peeing in the pool on occasion, according to the Water Quality & Health Council trade group.

Imagine what it might be like in a pool of adults and kids.

So, is your pool safe to swim in? Here are some things to think about and watch for, and a few ways to dip your toe to test the waters first.

Common sense

Chlorine and other chemicals are added to pools to keep the water clean and still swimmable. But the more people you put it a pool and the hotter it gets, the quicker the chemicals break down. State health rules are strict, and public pools are tested and inspected regularly.

You can help. Shower before swimming. Don't pee in the pool. Encourage young children to take regular bathroom breaks. Never go swimming after a recent bout of stomach distress.

Does the pool water look clear and blue? You should be able to see through the water down to the drain or stripes painted on the pool's floor. If the water is cloudy and colored, there may be algae in it, according to the American Chemistry Council.

Does the pool wall around the water line feel slimy? If it does, there are probably germs living on the wall.

Listen to make sure pool cleaning equipment is running. You ought to be able to smell the chlorine, but not too much.

One more glance

Chemical controllers are Matt Fagan's secret weapon, he likes to say. They are automated testing and cleaning-chemical installers that keep a pool's chlorine and acidity levels in balance, ensuring a clean pool. At his Sweetwater Pools, a commercial pool service based in North Charleston, staff is required by state law to do their own tests at least once per day.

Despite the controllers, the staff will test four times per day or more depending on the heat and how crowded the pool gets, he said.

"Clean water is not always a good indicator. There's no real way for a swimmer to tell about the water just by looking at it," he said.

Fagan has his own eyeball tip for people deciding whether a pool is clean: Look down. A pool that's dirty along the bottom hasn't been vacuumed, and might not be maintained well otherwise, he said.

The odds

Eight in 10 routine inspections of public pools turned up at least one health and safety violation, according to the federal Centers for Disease Control and Prevention in 2016.

One in eight of those had to be closed immediately.

One in every three swimming-related disease outbreaks occur at hotels, according to the CDC.

Those were pools in the most populated states. The best news here is that the S.C. Department of Health and Environmental Control stays on top of pool health issues, according to industry representatives.

"South Carolina is very stringent," said Susan Wichmann, an environmental health specialist with the National Swimming Pool Foundation. "They are very strict with their inspections, very strict with their pool operator certifications. That keeps a pool safer."

DHEC hires nearly 30 extra seasonal pool inspectors each year to work alongside a full-time staff of 21. They cite some 200 pool or spa facilities per year for health or safety violations, according to spokeswoman Cristi Moore.

The only type of facility cited more often is food establishments, which racked up 540 violations in 2017.

By comparison, there are fewer than 8,000 public swimming pools in the state. There are about 19,000 food facilities.

Code red?

In the pool service business, it's derisively called a "Code Brown." And not-so-potty-trained children are notorious for it, swim diapers or not.

Such diapers are not leak proof, the CDC notes. A lot of public pools nowadays confine diapered children to the kiddie pool, which is far easier and less costly to clean than a full-size pool.

Keeping the child out of the adult pool is the safest bet. At a minimum, the CDC also recommends frequent checks of the diaper.

Pools with a treatment issue are closed to get the shock treatment — a super dose of chlorine and other chemicals. The worst could end up drained for a scrubbing.

The CDC also recommends a regularly shocking at larger, more heavily used pools. The city of Charleston's four public pools, which average about 2,000 users per day per pool, get a shock every other Saturday, said J.J. Ayers-Millar, city of Charleston aquatics manager.

The chemical balance in the pools is checked multiple times during the day, she said.

"Unforeseen things inevitably happen," Ayers-Millar said. But because of the protocols "we don't have to shut down very often."

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Lifeguard and water safety instructor Jaime Stacy cleans the sides of the Martin Luther King Jr. swimming pool on Wednesday, May 23, 2018. "What you're doing is opening up the algae spores so the chlorine can do its job," said aquatics manager Jennifer Ayers-Millar. Wade Spees/Staff

Reach Bo Petersen Reporter at Facebook, @bopete on Twitter or 1-843-937-5744.

Science and environment reporter. Author of Washing Our Hands in the Clouds.