Super Shocking Your Pool – Part One

To understand the importance of super shocking your swimming pool it’s essential to understand the purpose of this periodic treatment in the first place. Super shocking your pool rids the water of organic compounds that can irritate swimmers and bathers with skin rashes and jock itch. These organic compounds prevent chlorine from performing its task as a sanitizer. Unfortunately, many pool service professionals and customers don’t have the time for this to be explained.

As hard as it may be to believe, many swimmers have complained about too much chlorine in public swimming pools when in reality the problem was that there was too little chlorine. Most noticeable is the odor of chlorine that you can smell before you ever even get in the water and then of course the red eyes and sore nose you experience after you’re in the water.

Why then, when you open a gallon jug of chlorine bleach or pool chlorine and take a whiff does it smell much fresher and cleaner than the odor that assaults us in public pools? This is because what you really smell is chloramine, the combination of chlorine and organic contamination; or bather waste. The truth is you actually smell an improperly sanitized pool that contains chemical compounds that need to be removed. Unfortunately, many pool employees add chlorine compounds when they shouldn’t. The chlorine compound forms hypochlorous acid also known as “free chlorine.” To disinfect or kill harmful microorganisms, pool employees often add chlorine. But the trouble is that “free chlorine” joins ammonia and nitrogen compounds forming combined chlorine and thereby hindering its ability to disinfect. What we need to do is rid the water of chloramines, a 3-step process.

First, you have to determine how much combined chlorine is in your pool’s water. You can use a DPD kit or test strip to determine the difference between the amounts of free and combined chlorine in your pool’s water. Adding the DPD # 1 tablet to the sample water will show you the free chlorine level in your pool’s water. Write down the result before adding the DPD #3 tablet to the same sample of water. This result is the total chlorine level in your pool’s water. If the total chlorine reading is higher than the free chlorine reading, then the combined chlorine in the water is the difference between the two. If the readings are the same then no combined chlorine is present.
Let’s say your test shows you have 1 ppm of combined chlorine in your pool. To get rid of the combined chlorine you’ll need to add 10 times as much free chlorine or 10 ppm. This process of organic waste destruction in water is known as “oxidation.” As you add more chlorine to pool or spa water that contains ammonia, the chlorine combines with the ammonia to form monochloramine. Adding chlorine to monochloramine and it forms dichloramine. Adding chlorine to dichloramine and it forms trichloramine. Add more chlorine to trichloramine and the trichloramine breaks down or oxidizes into simple nitrogen or chloride salt. At this point breakpoint chlorination occurs and any chlorine added after that is considered free chlorine as long as no new contamination occurs in your pool or spa.
Superchlorination, or super shocking your pool, is trickier than many people think. Add too much chlorine and it could take days to drop to a safe level but if not enough is added, you’ll have a combined chlorine problem that could lead to eye burn and skin irritation. In Part II we will discuss how to calculate how much of a given chlorine product you will need to provide the correct free chlorine level.

This entry was posted on Tuesday, July 10th, 2012 at 7:57 am and is filed under pool services. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.