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The Effect of Sunlight on Chlorine

Effect of Sunlight on Chlorine

From 2000 to 2014, 27,219 cases of waterborne illnesses in the US had to do with treated recreational water use. Those cases were part of 493 outbreaks, most of which occurred in the summer. From hotel swimming pools to hot tubs — these were the most common origins of the various diseases.

On top of all those illnesses were those caused by untreated recreational water use. Within the same period, swimming in untreated water led to 4,958 cases of diseases.

Most water-related diseases occur in the summer due to the effect of sunlight on chlorine. While an excellent disinfectant, the sun can also interfere with chlorine’s disinfection abilities.

Ready to learn how sunlight renders chlorine less effective in your pool water? Then let’s dive right into it!

The Effect of Sunlight on Chlorine: Degradation and Reduction

As little as two hours of sun exposure — that’s all it takes to reduce chlorine content by 90%. 

That’s because ultraviolet light is a type of electromagnetic radiation. This, in turn, makes it powerful enough to split apart chemical bonds. In pool chlorine, UV light breaks the bond of the substance’s hypochlorite ions.

Hypochlorite ions are the ions measured as free chlorine. In pool water, free chlorine is the “unused” portion of, say, liquid chlorine. However, because the sun’s UV rays break it down, the chlorine turns into a gas.

This gas then rises into the air instead of mixing with the pool water.

That’s why during super sunny days, you’d need to replenish your pool chlorine more often. At the same time, you need to ensure the efficient performance of your pool equipment. This is especially true for filtration units, which help to keep your pool water clean and clear.

More Sunlight Warrants More Frequent Chlorine Monitoring

Chlorine in swimming pools kills most of the pathogens that cause water illnesses. This is also why more than 98% of US water facilities use it as their primary water disinfection material. However, the actual time that chlorine needs to kill these harmful microorganisms varies.

For instance, free chlorine can kill E. coli in under a minute. However, it needs to be in your pool water for more than 45 minutes to kill Giardia. You also need free chlorine in your pool water for 11 straight days to kill Cryptosporidium.

Now, remember that UV radiation has a massive reducing effect on pool chlorine. So, you’d need to measure your pool’s disinfectant and pH levels more often in the day. From there, you can then apply more to meet the recommended pH and disinfectant levels.

This is even more important if you live in one of the sunniest parts of the country, such as Texas. The Lone Star State, in fact, has become the hottest state in the entire US.

That’s all the more reason to have your very own pool at home. However, it’s also why you should be more careful about your pool’s chlorine content.

Don’t Let the Sun’s UV Rays Keep You Away From Your Pool

There you have it, everything you need to know about the effect of sunlight on chlorine. The bottom line is, the sun’s UV rays can make chlorine disappear. That’s why you should think twice before jumping in your pool, no matter how tempting its clear water is.

Want to learn more about swimming pool construction or renovation in or around Houston, Texas? Then please feel free to get in touch with us here at Precision Pools & Spas! We’ll be happy to answer all your pool-related questions.

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