As we reported recently, the Centers for Disease Control and Prevention have found that an incredible 80 percent of public swimming schools had either health or safety violations, and a huge chunk of them were so bad they had to be shut down immediately. But why has the public pool situation gotten so bad, and what can you do to protect yourself? Fortunately, it’s pretty simple.

For the study, the CDC examined Arizona, California, Florida, New York, and Texas because they are the five state with the most public swimming pools. Eight out of every 10 pools had violations, and one out of every eight had violations so severe they required an immediate shutdown.

Not all of them are due to contaminants — some are safety issues like failing to have proper safety equipment on hand. But a lot of the violations were because of contaminated waters, particularly in children’s wading pools where young children are more likely to swallow water and therefore contract an illness. A total of 350 disease outbreaks have been linked to public swimming pools between 2003 and 2012.

How did they get this bad? The report found that public swimming pools often weren’t putting enough disinfectant in the water, like chlorine. As a result, pools are often becoming a breeding ground for disease and germs.

But it’s not just the disinfectant concentration, it’s also the level of pH at the pool that matters. Improper pH at 15 percent was actually a more common violation than disinfectant concentration, which was the case 12 percent of the time.

How can you protect yourself and your children? It’s actually quite simple: buy a test strip either at a superstore or online. You can dip this in the water to determine the pH and free chlorine or bromine concentrations. You should be looking for a free chlorine concentration of at least 1 ppm in pools and 3 ppm in hot tubs and spas. For bromine it’s 3 and 4, respectively. The pH should be between 7.2 and 7.8.