What is "CC"?

What is CC??

Combined chlorine... This is chlorine that registers as part of Total Chlorine in an ODO test kit, but it has already combined with contaminants in the water so it is not available for sanitation (it's used up). CC is also what is responsible for the "chlorine odor" in pools and eye/skin irritation.

CC = combined chlorine. Combined chlorines are also often referred to as chloramines.

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When FC (free chlorine) interacts with various bits of dirt and goo in the pool (including germs), it does so by chemically reacting with various compounds in the 'goo'. This reaction tends to destroy the goo, and convert the chlorine (Cl+) to salt (Cl-), as in sodium chloride (NaCl). SWCGs (Salt Water Chlorine Generators) work by reversion this conversion, changing chloride (Cl-) into free chlorine (Cl+).

However sometimes the process of reacting with goo does not 'go all the way', but only goes half way. The results are compounds that are sorta like free chlorine, but also sorta 'goo-ish'. The very simplest of these compounds are those that form when chlorine reacts with ammonia, and forms monochloramine (NH2Cl), dichloramine (|NHCl2) or nitrogen trichloride (NCl3). These are combined chlorine (CC), or chloramines.

The problem with these products is that (a) they are irritating to people, (b) they stink and make the pool smell 'like chlorine', and (c) they are not as good at sanitizing as chlorine. So, the pool industry has promoted a tactic to get rid of these compounds, called 'superchlorination' or 'breakpoint chlorination' or 'shocking'. Of those three terms, only "breakpoint chlorination" has an actual specific definition; the other two terms mean whatever the person using them means. Usually, they mean "raising chlorine levels higher than usual", but they can mean other things, as well.

The problem with this tactic is that it only works with the simple chlorine-ammonia compounds, but those compounds are only RARELY the actual CCs found in pools.

There are two exceptions.

1. Ammonia is sometimes added directly to pools, usually as a sort of an algaecide. "Yellow OUT" and "Mustard Master", among other products, are mostly ammonium chloride. Use these in your pool, and you'll end up with chlorine-ammonia compounds that respond to "breakpoint chlorination". Use them correctly, and you'll mostly end up with monochloramine -- which is a poor sanitizer, and rather irritating, but an excellent algaecide -- instead of dichloramine or nitrogen chloride, both of which are real problems.

2. Stabilizer can be 'eaten' by bacteria. Often, when this happens, the stabilizer is converted to nitrogen gas and simply disappears. But sometimes, it's converted to ammonia . . . and 100 ppm can be bacterially converted to a LOT of ammonia. This situation gives rise to the posts here where "my pool is clear, and all the algae is gone, but I have no stabilizer and the chlorine disappears almost as soon as I add it".

But, outside of these exceptions, the ACTUAL chloramines in your pool tend to be more complex. For example swimmers urine + chlorine can result in N-chlor-urea and many other compounds. These chloramines -- the ones actually in your pool -- do NOT respond to the neat hump & dip breakpoint chlorination which is the basis for many of the recommendations for shocking used by the pool industry. Instead, they can be removed, at least on outdoor pools, with the combination of solar UV and consistent and adequate chlorine levels -- no shocking needed.

'Shocking' may be necessary to help remove established algae, but is NOT needed to remove CC's