Is it Safe to Swim in a Pool with Algae?

Is it Safe to Swim in a Pool with Algae?
by Mark Garcia June 14, 2019

green algae pool istk

Can you swim in a pool that has algae? Green pool water is no less refreshing than blue pool water, still feels great on a hot day.

And don't we swim and water ski on green-ish lakes, or walk over algae covered river rocks, or ride ocean waves with marine algae? 

So it begs the question, usually from the children of the home, ''Why can't we swim in green pool water?!?''


Pools Aren't Small Ponds

There is a major difference between pools and lakes, one that makes it OK to swim in a green lake, but not a green pool. Pools are closed systems, and other than occassional rain water or refill water, they are not continuously diluted. They also do not have a balanced ecosystem, like lakes or ponds with microscopic aquatic life, and plants that actually clean the water of toxins and bacteria. A pool is actually closer to a swamp than it is to a pond. 


Where there's Algae, there's Bacteria

Algae is not harmful by itself, and I've heard that for many people algae is a delicacy, and quite nutritious. It's what you don't see however, that could make you sick. If there is not enough chlorine to kill the algae, there is certainly not enough chlorine to kill bacteria, viruses, parasites and other pathogens, which could possibly also be in the water. These can enter the body of a swimmer via a small skin cut, or through eyes, ears, nose and throat. The result of swimming in a green pool could be ear infections, fever, diarrhea and other summer bummers.


When can we Swim, Then?

When your pool has lost most of the green tint, and your chlorine level is holding, or staying constant in a range of 1 to 5 ppm, and your chloramine level (combined chlorine) is near zero. Double check the pH and alkalinity, and be sure the chlorine level is below 5 ppm. Even if the water is not completely clear, but more of a cloudy blue-ish color, you could allow limited swimming. If the water is so cloudy that you cannot see the pool bottom however, that poses several safety risks for swimmers.

And if you have recently shocked the pool with granular chlorine, follow the label instructions about when it's safe to swim. Undissolved granules could irritate the eyes and skin of swimmers. Some pool shock products are ''swim immediately'', and others suggest a 12-24 hour waiting period before swimming.

And people please, remember to run your filter system 24/7 when trying to clean up algae or cloudy water. Don't worry - it won't explode! Just check on it 2-3 times per day, and backwash when the pressure gauge is 7-10 lbs over clean. 2 to 3 days after a hard shock treatment, you can begin to use algaecides and clarifiers, per label instructions, to help out your filter and help prevent a re-bloom of algae. If your filter is really struggling with clearing the water, you may need new filter sand or cartridge, or a larger pool filter



Now then, I think I've made my point - that is, Don't Swim in a green algae pool; and not because of the algae, but because of the possibility of pathogens also found in the pool water. Sickness is not guaranteed, but to answer the question posed at the top of the page - sorry kids, it is not safe to swim in a green pool.

If you must swim in a green pool however, I'd suggest keeping heads above water at all times, and taking a shower after you enjoy a very short swim.


Thanks for Reading!

Mark Garcia