The Difference Between Free and Total Chlorine

From Swim University

Most people when they are swimming in an inground pool are congnizant of one aspect of water chemistry: Chlorine Level.  What people don't realize is that this seemingly simple measure is actually quite complicated.  It takes an amateur chemist to understand water balance, and all of the various factors that can affect it in swimming pools.  This post by Matt Giovanisci of Swim University, however, attempts to explain the components of chlorine within that complicated mixture.  

Here is an excerpt from the post:

Water Chemistry

From 1 Stop Pool Pros

It's easy to assume that a swimming pool is "set it and forget it", but that really is not the case.  Anyone familiar with swimming pool water chemistry understands that to achieve balanced, healthy water, one needs to understand the differing measurable components of the water saturation index.  The important levels of pH, Alkalinity, Hardness, Temperature and Free Available Chlorine are all integral to achieving a safe, sanitary swimming pool environment.  This post from 1 Stop Pool Pros gives a good primer on the different chemicals that are utilized to achieve balanced water in these important areas.

Here is an excerpt from the post:

Chlorine: The Cause of Irritated Eyes of Swimmers?

From Healthy Pools

The most common misconception surrounding swimming pools is the cause for the "Chlorine" smell, eye and skin irritation, and skin disorders.  A properly chlorinated pool will not smell, will not irritate eyes, and will not be a catalyst for spreading disease.  The concept, simply put, is that chlorine has three distinct components that determine it's killing capacity:  Total Chlorine, Free Chlorine, and Combined Chlorine.  Combined Chlorine is the culprit, and is caused by the chemical reaction that occurs when chlorine actually does it's job.  This post from Healthy Pools expounds on this concept, and busts an often perpetrated urban legend around chlorine and swimming pools.

Here is an excerpt from the post:

The Chlorine Myth / What creates that chlorine smell

To some people chlorine is the devil, its the worst. Maybe they saw an episode of 20/20 that said "Chlorine, The Silent Cleanser." Well it's not as bad as you may think, in fact its the best thing for you and we are here to clear all charges against chlorine.

Myth: Chlorine Burns Your Eyes When You Open them Underwater

Fact: Low pH burns your eyes when you open them underwater. A pool that has low pH means that the water is acidic. When water is acidic, its like putting your tongue on a battery (though not as harsh) but if you expose your eyes to it then yes, it's gonna burn. You could have a chlorine reading of 10 ppm (Parts Per Million) and as long as your pH is ok, then your eyes will be ok.

Myth: Chlorine can do long term damage on my filter system

Fact: No it can't, but low pH can corrode metal and high pH can leave a hard deposit. We can simply say that most problems that are associated with chlorine are really the fault of chlorine. The only thing bad about chlorine is that you can't eat it, or can you?

How Germs Get In The Swimming Pool, Scientific American via Huffington Post

By Larry Greenemeier

(Click here for the original article)

As the summer winds down and Labor Day weekend approaches in the U.S., beaches and public pools will be filling up with swimmers looking to take one last dip outdoors before the season ends. Most people will hit the water without worrying about the microscopic organisms they'll be swimming with. Maybe that's for the best, considering what those organisms are and how they're introduced to swimming holes.

The protozoan organism Cryptosporidium, one of the most frequent causes of waterborne disease, has become a major problem in swimming pools, says Charles Gerba, a microbiologist at the University of Arizona who's spent decades studying how pathogens are transmitted. Crypto is a microscopic parasite with a tough outer shell that allows it to survive for days even in properly chlorinated pools.