So… why did the Rio Olympic pool turn green??

Remember when that giant Olympic pool turned green overnight in Rio? It took nearly a week to determine the actual cause of the sudden discoloration, and this was a pool with very high-tech chemical monitoring systems!

While very few pool owners own these monitoring systems, almost every one of them has experience green pool water. So what happened to it?

The first explanation was that an algae bloom had occurred due to low chlorine levels and the result of having so many swimmers use the pool, but it was announced that the chlorine levels were fine. Then they said it might have been metals in the water, but announced the levels of metals was also fine. Then they said it might be the alkalinity levels reacting with chlorine… again, fine. Finally, about a week after the discoloration, it was announced that 160 liters of hydrogen peroxide was added to the pool, which “neutralized” the chlorine and allowed for growth of organic matter such as algae.

Sounds like they finally figured it out, right? Well, not so fast. As many experienced chemists and pool experts have noted, hydrogen peroxide will not neutralize chlorine, but will instead gradually decrease chlorine levels… but the Rio officials claimed that the chlorine levels were in the correct range the entire time!

We’d love to give you an answer to what exactly happened, but instead of figuring it out and treating it, Olympics officials did the quick solution and simply drained and refilled the pool water.

Here at The Swimming Pool Store, we aren’t going to judge those in charge of keeping the Rio pool clean and clear. We know there are many different ways pool water can turn green. And we know how hard it can be to diagnose a green pool. But we do feel a little better knowing that it could happen on even the biggest stages!