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by Dion Rodrigues

Avoid Green Pools with this information

Water was a concern heading into the Olympics in Rio de Janeiro. Visible garbage and sewage raised concerns about athletes competing in waterways surrounding the city. Last week, however, attention shifted to pool water. Overnight the Olympic diving pool transformed from a clear blue to a murky green.

So what happened? After some confusion Rio officials have confirmed exactly what happened. And it’s a lesson that pool owners should take to heart.

The Cause

Savvy pool owners might have assumed that the green and murky water resulted from algae growth. Initially algae was a suspected cause, but officials also suspected “a fall in alkalinity,” which would explain how the water colour could change so quickly, and why the neighbouring pool remained unaffected.

A few days later, with the neighbouring pool showing a similar greenish hue, the true cause was announced. Algae. But the root of the algae growth is something pool owners should pay particular attention to. A contractor working on the pool added a large amount of hydrogen peroxide, which is a de-chlorinating agent. The overuse of the hydrogen peroxide effectively cancelled out the chlorine already in the pool, allowing the algae to grow freely.

The lesson: know exactly what chemicals are going into your pool and check levels regularly.

The Effect


Sure Brazil’s embarrassment is on the world stage, but it’s certainly relatable to the average pool owner. Imagine inviting your friends and neighbours over for a swim and finding your pool, which was clean yesterday, is now discoloured and foul smelling.


With a need to press on with the events as scheduled, the Rio Olympic organizers were forced to drain the pool. The process totalled ten hours and wasted almost a million gallons of water.

Algae in your pool wouldn’t require such extreme measures to clean, but you would need to spend hours to treat your water with algaecide and scrub your pool’s bottom and sides – a chore no one wants to add to their “to-do-list”.


This sudden change in the water raised safety concerns. Chlorine kills pathogens in your pool and algae growth indicates that these pathogens are not being dealt with. On the other hand, excessive chlorine can cause severe irritation to swimmer’s eyes and skin.

The Solution

Regular maintenance and prevention is the solution. Learn from the slow response of Rio officials. By sticking to your maintenance routine and preparing yourself by being well stocked on pool supplies you can prevent algae growth, or respond quickly with the pool supplies you have on hand.

Include a pool water test kit in your on-hand pool supplies. Testing the water regularly and often will help you avoid the chemical issues that turned the Rio Olympic pool green. Once you identify an imbalance in your pool’s chemistry you can be confident in applying the correct chemicals to maintain a safe and clean pool.

You also need to keep your pool water clean. For that you need to skim and vacuum your pool regularly. Tech enthusiasts can have fun with this aspect of pool maintenance by exploring fully automated options.

If, despite these steps you have algae growth in your pool make sure you check your pool equipment and apply algaecide as needed. You’ll be swimming again in no time!