Why the Olympic pool water went green – and how to avoid it!

If, like us here at UK Pool Store, you can’t take your eyes off the Olympics again this year (and of course especially the swimming pool based events) you’ll have noticed recently that the pool water degenerated from crystal blues to murky greens. Two of the pools in Rio succumbed, with some athletes complaining that they can’t even open their eyes properly. Of course, the Olympic officials told the competitors that the water was safe, but what exactly happened here and what as pool owners can we learn from it? I can’t remember seeing water like that at the Olympics before and personally I don’t think it’s good enough.


Photo by Adam Pretty/Getty Images

FINA (The international governing body of swimming) recently stated that the reason behind the green is that they were short of the necessary chemicals; here’s that FINA statement:

“FINA can confirm that the reason for the unusual water color observed during the Rio diving competitions is that the water tanks ran out of some of the chemicals used in the water treatment process.

As a result, the pH level of the water was outside the usual range, causing the discoloration. The FINA Sport Medicine Committee conducted tests on the water quality and concluded that there was no risk to the health and safety of the athletes, and no reason for the competition to be affected.“

Aside from FINA’s explanation, another article I read said that pH levels had been imbalanced caused by the amount of athletes using the pool. This, according to their theory, had caused copper levels to spike, making the water appear more green. An interesting idea, and certainly copper in the water would cause a green colour, but the amount of copper to cause a pool of that size to turn would most likely kill the athletes; I’d doubt it’s that. I’d also be surprised that the usage of the pool would be affecting things here, it’s not like those responsible didn’t know how many athletes they’d have using the pool.

In UK Pool Stores’ opinion – FINA are wrong. For the pools to be going green at this rapid pace, it had to be algae. Algae can multiply at 100 times per hour, in a pool that size, it can take over quickly. With that in mind, FINA’s statement that they didn’t have enough chemicals would be accurate. I said to someone in the office last week that the only way forward is to flush the pool with an incredible high amount of chlorine to deal with the algae, and then use hydrogen peroxide to neutralise the high levels of chlorine. Of course, this isn’t ideal when a pool is in constant use at the World’s most highly viewed sporting event.

Since this has happened, we’ve heard stories that a worker had accidentally used hydrogen peroxide in the first place, which lead to the algae outbreak. Luckily for the athletes, the pool water is back blue again – it seems like they’ve drained the pool and started again.

For you at home, draining the pool and starting again isn’t exactly the ideal option, so below is a few key elements that are great for keeping your pool in tip top condition. Just remember not to accidentally put a load of hydrogen peroxide in!

A Good Filtration System Allows for good circulation, 24 hours a day, keeping water clear and clean.

An Automatic Pool Cleaner – Allows you to have mechanical abrasion where algae would start to take hold – the more bacteria and debris that’s removed, the less chance of algae taking hold.

Water Testing Equipment – Help to keep your pool as close to 7.2pH as possible – this helps to increase the chlorine kill rate.
Swimming Pool Chemicals – Keep your chemical stores fully stocked!

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