The Effect the Sun Has on Chlorine

Posted by Tim Roadnight
The effect the sun has on chlorine

The Effect the Sun Has on Chlorine

You’ve probably heard sunlight affects chlorine levels in your pool. But, have you ever wondered what the effect the sun has on chlorine and why? There are several chemical reactions that occur when chlorine molecules are exposed to ultraviolet radiation from sunlight and high summer temperatures. We explain that process here, so you can take appropriate action and enjoy your pool, even when the mercury is climbing.


Chlorine 101

Without chlorine added, your swimming pool would be full of bacteria and algae. The water would be unhealthy. You would be able to recognize there’s a problem because the water would be a cloudy greenish color.

Chlorine disinfects the water you are swimming in through the use of a process where the chemical reacts with lipids that make up the cell walls of the bacteria and algae. The cell membranes are ruptured and the unwanted organisms are killed.

To accomplish this feat, a potent chemical, such as chlorine is required. Careful monitoring is necessary to make sure your pool always contains the correct amount of chlorine. Too little, and your pool becomes laden with bacteria and other unwanted guests. Too much, and your skin and eyes can become very irritated.

To keep proper water balance, both free chlorine and combined chlorine are measured. If the free chlorine level is below 1 ppm, the pool isn’t safe to swim in. Think of combined chlorine as the same chemical that has combined with pesky bacteria and algae, and is, in a sense, used. A large amount of combined chlorine indicates your pool is flooded with too many unwanted invaders.


Chlorine Sunlight Reaction

We provided the brief explanation above to illustrate the importance of free chlorine, which is lost when it combines with unwanted organisms. But, are there other factors? What depletes chlorine in a pool? Chlorine reacts when it’s hit by sunlight and by scorching summer temperatures.

Here’s what happens when chlorine is hit by sunlight: Hypochlorite ions are formed in the water. It’s what is measured as free chlorine. The problem is the effects of UV radiation. When ultraviolet radiation from the Sun reaches a hypochlorite ion, it falls apart on a molecular level. It turns into a gas that’s released into the atmosphere.

Chlorine degradation in sunlight is surprisingly high. How fast does chlorine evaporate from a pool? Just two hours of sunlight on a beautiful day can reduce the chlorine level in your pool by as much as 90 percent. That’s why you see pool service technicians adding chlorine and stabilizers regularly. But, chlorine degradation in sunlight isn’t your pool’s only enemy. Heat plays a part, too.


Does Water Temperature Affect Chlorine?

High temperatures also indirectly break down chlorine. Since most bacteria grow more readily in warm water, when there’s an increased number of bacteria in the pool water, more free chlorine becomes combined chlorine. Basically, the chlorine is used up.

When temperatures are climbing, there is a general rule. You should add twice as much chlorine to the water to maintain free chlorine levels for every 10 degrees Fahrenheit the temperature climbs above 80.

With so many things working against free chlorine, including sunlight, heat, bacteria, and algae, you may begin to wonder if there’s anything that can be done to protect chlorine levels. This protective effect is provided by cyanuric acid. Ask your pool service professional about chemical compounds, such as dichlor and trichlor, which release cyanuric acid into the pool. This will maintain proper chlorine levels, so you can enjoy those hot, sunny days without worrying about chlorine levels.

Feel free to contact the pool service specialists, Pool Knights. We will be happy to assist you regarding your personal pool maintenance needs and questions.