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What’s the Difference Between Free Chlorine and Total Chlorine?

The day has finally come… you are the proud owner of a new swimming pool!  With the enjoyment of your new pool also comes the responsibility of checking chlorine levels and proper maintenance. It doesn’t always take long for pool owners to feel overwhelmed and confused by the details of maintaining the proper levels in their pool.

The Use of Chlorine in a Pool

Each time your pool is used different organic matter is being added to your water; this can be anything from dead skin cells to lotions and everything in between. To keep pool water clean, chlorine is added into the pool. The chlorine works to eliminate the organic matter thus cleaning your pool water. Pool owners check the levels of the pool frequently to make sure that there is enough chlorine working in the pool to keep the water clean and safe. There can actually be three types of chlorine in your pool at any given time: free chlorine, combined chlorine and total chlorine. Pool With Sparkling Clear Water

What is the difference in free and total chlorine?

Free Chlorine When you add chlorine into your pool it mixes with the pool’s water to form hypochlorous acid and hypochlorite ions. Together, these are known as “free chlorine”. Free chlorine is the chlorine that is active in your pool and ready to go to work eliminating contaminates in your pool. This type of chlorine is still unused and what you typically test for in your pool.   Combined Chlorine Once the free chlorine has been used and reacts with contaminates like ammonia or nitrogen in the water, it becomes combined chlorine. This used chlorine will still show on tests as being present in your pool water, but it is unable to do the same job as free chlorine because it has already been partly used up. Combined chlorine can be as much as 60% to 80% less effective than free chlorine. When you can smell “chlorine” in the water, you are actually smelling the combined chlorine. A properly chlorinated pool will not smell like chlorine. Total Chlorine Once you know the meaning of free chlorine and combined chlorine the name of “total chlorine” pretty much says it all. Total chlorine is the total amount of chlorine that is in your pool water, including free chlorine and combined chlorine. Many pool experts use this simple equation:

Free Chlorine (FC) + Combined Chlorine (CC) = Total Chlorine (TC)

Therefore, the level of total chlorine in your pool will always be greater than or equal to the level of free chlorine in your pool. The difference between the two lets you know how much chlorine is in your water that has already been used and turned into combined chlorine.   Maintaining chlorine levels To make sure that you have enough free chlorine in the water to remove the combined chlorine, you need to determine the amount of combined chlorine in your pool and then add 10 times the amount of free chlorine. This will help to keep your pool water at its best and let you enjoy being a pool owner on these hot summer days.

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