Below is a direct copy and paste from the Centers for Disease Control and Prevention website regarding protection against Recreational Water Illnesses.
Steps of Healthy Swimming: Protection Against Recreational Water Illnesses (RWIs)You can choose to swim healthy! You have the power to help keep germs out the water in places we swim in the first place. Remember, chlorine and other disinfectants don’t kill germs instantly. Additionally, the mixing of chlorine with pee and sweat uses up the chlorine in the pool, which would otherwise kill germs. We all share the water we swim in, and each of us needs to do our part to help keep ourselves, our families, and our friends healthy. To help protect yourself and other swimmers from germs, here are a few easy and effective steps all swimmers can take each time we swim:
Keep the pee, poop, sweat, and dirt out of the water!
Stay out of the water if you have diarrhea.
Shower before you get in the water.
Don’t pee or poop in the water.
Don’t swallow the water.
Every hour—everyone out!
Take kids on bathroom breaks.
Check diapers, and change them in a bathroom or diaper-changing area–not poolside–to keep germs away from the pool.
Drink plenty of fluids.
Check the free chlorine level and pH before getting into the water.
Pools: Proper free chlorine level (1–3 mg/L or parts per million [ppm]) and pH (7.2–7.8) maximize germ-killing power.
Hot tubs/spas: Proper disinfectant level (chlorine [2–4 parts per million or ppm] or bromine [4–6 ppm] and pH [7.2–7.8]) maximize germ-killing power.
Most superstores, hardware stores, and pool-supply stores sell pool test strips.