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| − | ==What is | + | [[Category:Swimming Pool Chemistry]] |
| − | “Combined | + | ==What is Combined Chlorine in a Pool?== |
| + | “Combined Chlorine” is a generic chemical term for chemical compounds formed from the reactions of chlorine with organic and biological contaminants in pool water. | ||
| − | Chlorine, | + | Chlorine is a potent oxidizer, specifically the active chlorine compound hypochlorous acid (HOCl). Oxidizers, in chemical terms, take electrons away from the molecules that they oxidize and, in the process, break those molecules down into different compounds. The most common forms of combined chlorine found in swimming pools are those compounds where chlorine has reacted with nitrogen-containing chemicals in human bather waste (sweat, urine, etc). |
==What are Chloramines in Pool Water?== | ==What are Chloramines in Pool Water?== | ||
| − | These chlorine-nitrogen compounds are called “chloramines” and there are three primary types - monochloramine, dichloramine and nitrogen trichloride. Chlorine can also react with urea | + | These chlorine-nitrogen compounds are called “chloramines” and there are three primary types - monochloramine, dichloramine and nitrogen trichloride. Chlorine can also react with urea to form monochlorourea and related compounds. |
| − | + | Many other types of chlorinated organic compounds can form, and not all of them show up on a combined chlorine test. Combined chlorine compounds irritate mucous membranes and have relatively low odor thresholds. | |
| + | |||
| + | ==What Are Persistent Combined Chlorine in Hot Tubs?== | ||
| + | |||
| + | Hot tubs eventually build up chemical waste called persistent combined chlorine compounds or persistent CCs. No amount of chlorine you can add, within reason and safe for your tub, will break them down. Without much sunlight and even under low load, persistent CCs are always possible.<ref> https://www.troublefreepool.com/threads/cant-get-cc-below-0-5-ppm.248940/post-2180921 </ref> | ||
| + | |||
| + | To clear persistent CCs, you need to purge the plumbing with Ahhsome, drain, wash down, and suction out as much water from the plumbing as possible, and then refill. Hot tub water shouldn’t be left for more than 2-3 months before draining it. | ||
==Why Do CCs Test in Drinking Water== | ==Why Do CCs Test in Drinking Water== | ||
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Chloramines that appear as CCs are added to municipal water in some areas. | Chloramines that appear as CCs are added to municipal water in some areas. | ||
| − | Chloramines (also known as secondary disinfection) are disinfectants used to treat drinking water and they: | + | Chloramines (also known as secondary disinfection) are disinfectants used to treat drinking water, and they: |
*Are most commonly formed when ammonia is added to chlorine to treat drinking water. | *Are most commonly formed when ammonia is added to chlorine to treat drinking water. | ||
| − | *Provide longer-lasting disinfection | + | *Provide longer-lasting disinfection as the water moves through pipes to consumers. |
| − | + | Water utilities have been using chloramines since the 1930s. More than one in five Americans uses drinking water treated with chloramines. | |
| − | For more information see [https://www.epa.gov/dwreginfo/chloramines-drinking-water US EPA - Chloramines in Drinking Water]. | + | For more information, see [https://www.epa.gov/dwreginfo/chloramines-drinking-water US EPA - Chloramines in Drinking Water]. |
==What causes that Chlorine Smell in Pools?== | ==What causes that Chlorine Smell in Pools?== | ||
| − | Combined chlorines are responsible for that “gross chlorine pool | + | Combined chlorines are responsible for that “gross chlorine pool smell,” which is a good sign that the pool water from which it comes is not correctly maintained. Properly chlorinated pool water with the [https://www.troublefreepool.com/content/134-recommended-levels recommended levels] of [[Free Chlorine]] and low to no combined chlorine has no smell to it…the nose knows, as they say! |
| − | ==How Do You | + | ==How Do You Test For Combined Chlorines?== |
| − | High quality pool water test kits test for both FC and CC. Because of the nature of the CC test, it is mostly sensitive to | + | High-quality pool water test kits test for both FC and CC. Because of the nature of the CC test, it is mostly sensitive to simple chloramines but not all chlorine-containing organic compounds. |
| − | The CC concentration in a clean swimming pool should be very low (< 1ppm and very often near 0). Many CCs are further oxidized and destroyed by UV light and are | + | The CC concentration in a clean swimming pool should be very low (< 1ppm and very often near 0). Many CCs are further oxidized and destroyed by UV light and are pretty volatile compounds (they will naturally outgas from pool water), |
| − | It is possible to detect high levels of CCs temporarily in pool water and the CC level will fluctuate from time | + | It is possible to detect high levels of CCs temporarily in pool water, and the CC level will fluctuate from time to time. Still, any prolonged measure of CCs above 1ppm indicates a problem with the pool water being tested. |
| − | Water | + | Water suffering from an algae bloom, being treated to destroy algae, or having had a high bather load will often generate high CCs while the free chlorine is disinfecting pathogens and oxidizing bather waste. Eventually, though, the CCs of a clean pool should be below 0.5 ppm most of the time. |
==What are Other Sources of Combined Chlorines in Pool Water?== | ==What are Other Sources of Combined Chlorines in Pool Water?== | ||
| − | Some chemical compounds, such as potassium monopersulfate (a | + | Some chemical compounds, such as potassium monopersulfate (a standard non-chlorine shock used in hot tubs and sold in products like Oxibrite) or sulfamic acid (an organic acid used to remove calcium and metal scale) will show up on the chlorine tests as CCs. |
| + | |||
| + | Free Chlorine testing after using Sulfamic Acid is discussed in [[Acid#FC_Testing_After_Using_Sulfamic_Acid]]. | ||
| + | |||
| + | Potassium Monopersulfate Compounds, aka MPS or "non-chlorine shock' will interfere with the [[CC|Combined Chlorine]] test.<ref>https://taylortechnologies.com/en/page/141/eliminating-interference-from-potassium</ref> Taylor Technolgies has the R-0867 Deox Reagent that will neutralize MPS effects on the CC test. R-0867 Deox Reagent is available in the [https://taylortechnologies.com/en/product/test-kits/reagent-packmonopersulfate-interference-remover-for-2000-series-kits-w-75oz-rea--K-2041 K‑2041 (.75 oz)] and [https://taylortechnologies.com/en/uproduct/reagent-pack-monopersulfate-interference-remover-for-2000-series-kits-w-2-oz-re?id=K-2042 K‑2042 (2 oz)]. It’s also available as a stand-alone kit, the [https://taylortechnologies.com/en/product/test-kits/drop-test-chlorine-freecombinedmonopersulfate-fas-dpd-1-drop-02-ppm--K-1518 K‑1518 FAS-DPD chlorine/monopersulfate test]. | ||
==Why Do I Have Algae With a CC of 0?== | ==Why Do I Have Algae With a CC of 0?== | ||
| − | Plants | + | |
| + | CCs are a sign that nitrogen-based substances like ammonia or urea have reacted with chlorine and formed "combined chlorine." A certain amount of "free chlorine" is then needed to complete the oxidation process, which ends with nitrogen gas being released. | ||
| + | |||
| + | CCs are common in pools with a high bather load. They are usually more of a problem in public pools than in residential pools, especially when following the TFP protocol because there's always enough FC to quickly deal with the little CC that forms. Maybe after a big pool party, especially with little kids involved who have too much FOMO to go to the bathroom. | ||
| + | |||
| + | Plants like algae create chemicals like glucose from carbon dioxide and water. Using light, the carbon in carbon dioxide oxidizes the oxide into oxygen.<ref>https://www.troublefreepool.com/threads/visible-algae-but-with-cc-of-0-im-confused.194376/post-1713538</ref> | ||
6CO2 + 6H2O --> C6H12O6 + 6O2 | 6CO2 + 6H2O --> C6H12O6 + 6O2 | ||
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Carbon dioxide + water--> glucose + oxygen. | Carbon dioxide + water--> glucose + oxygen. | ||
| − | This is how plants make oxygen and store energy in sugars. Most of the bulk of plants is carbon from carbon dioxide | + | This is how plants make oxygen and store energy in sugars. Most of the bulk of plants is carbon from carbon dioxide, and most of a tree's weight comes from the air. |
The carbon in carbon dioxide is in the +4 state. | The carbon in carbon dioxide is in the +4 state. | ||
| − | The carbon in glucose is 4 at 0, 1 at -1 and 1 at +1. The carbon is "reduced" | + | The carbon in glucose is 4 at 0, 1 at -1, and 1 at +1. The carbon is "reduced," which is the opposite of oxidized. Reduced just means that the oxidation state is lower or reduced because the atom gained negatively charged electrons. |
| − | When chlorine oxidizes the carbon in glucose back to a +4 oxidation state, it reverts | + | When chlorine oxidizes the carbon in glucose back to a +4 oxidation state, it reverts to carbon dioxide. |
| − | This is | + | This is similar to an animal using oxygen to burn sugars to release energy and exhale carbon dioxide. |
| − | So, chlorine reacting with algae is mostly an oxidation reaction | + | So, chlorine reacting with algae is mostly an oxidation reaction, not a combination. Algae is converted chiefly back into carbon dioxide and water. |
| − | Chlorine can combine with carbon compounds, such as methane (CH4) by replacing the hydrogen ions. | + | Chlorine can combine with carbon compounds, such as methane (CH4), by replacing the hydrogen ions. |
Carbon in methane is in the -4 oxidation state. | Carbon in methane is in the -4 oxidation state. | ||
| − | Algae | + | Algae mainly does not create CCs. |
| − | CCs are | + | CCs are created mainly by compounds like ammonia, where the nitrogen is in the -3 state. For ammonia, you get combination and oxidation. So, the CCs eventually go away, especially in sunlight, where UV photons knock loose electrons from the nitrogen and make it easier for the chlorine to take them. |
Active chlorine is +1, so it bonds with more negatively charged atoms, like nitrogen in the -3 state or carbon in the -4 state. | Active chlorine is +1, so it bonds with more negatively charged atoms, like nitrogen in the -3 state or carbon in the -4 state. | ||
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The carbon in algae has a zero net charge. | The carbon in algae has a zero net charge. | ||
| − | So, the reaction of chlorine with algae is mostly oxidation and not combination | + | So, the reaction of chlorine with algae is mostly oxidation and not a combination. |
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Latest revision as of 03:20, 21 November 2024
What is Combined Chlorine in a Pool?
“Combined Chlorine” is a generic chemical term for chemical compounds formed from the reactions of chlorine with organic and biological contaminants in pool water.
Chlorine is a potent oxidizer, specifically the active chlorine compound hypochlorous acid (HOCl). Oxidizers, in chemical terms, take electrons away from the molecules that they oxidize and, in the process, break those molecules down into different compounds. The most common forms of combined chlorine found in swimming pools are those compounds where chlorine has reacted with nitrogen-containing chemicals in human bather waste (sweat, urine, etc).
What are Chloramines in Pool Water?
These chlorine-nitrogen compounds are called “chloramines” and there are three primary types - monochloramine, dichloramine and nitrogen trichloride. Chlorine can also react with urea to form monochlorourea and related compounds.
Many other types of chlorinated organic compounds can form, and not all of them show up on a combined chlorine test. Combined chlorine compounds irritate mucous membranes and have relatively low odor thresholds.
What Are Persistent Combined Chlorine in Hot Tubs?
Hot tubs eventually build up chemical waste called persistent combined chlorine compounds or persistent CCs. No amount of chlorine you can add, within reason and safe for your tub, will break them down. Without much sunlight and even under low load, persistent CCs are always possible.[1]
To clear persistent CCs, you need to purge the plumbing with Ahhsome, drain, wash down, and suction out as much water from the plumbing as possible, and then refill. Hot tub water shouldn’t be left for more than 2-3 months before draining it.
Why Do CCs Test in Drinking Water
Chloramines that appear as CCs are added to municipal water in some areas.
Chloramines (also known as secondary disinfection) are disinfectants used to treat drinking water, and they:
- Are most commonly formed when ammonia is added to chlorine to treat drinking water.
- Provide longer-lasting disinfection as the water moves through pipes to consumers.
Water utilities have been using chloramines since the 1930s. More than one in five Americans uses drinking water treated with chloramines.
For more information, see US EPA - Chloramines in Drinking Water.
What causes that Chlorine Smell in Pools?
Combined chlorines are responsible for that “gross chlorine pool smell,” which is a good sign that the pool water from which it comes is not correctly maintained. Properly chlorinated pool water with the recommended levels of Free Chlorine and low to no combined chlorine has no smell to it…the nose knows, as they say!
How Do You Test For Combined Chlorines?
High-quality pool water test kits test for both FC and CC. Because of the nature of the CC test, it is mostly sensitive to simple chloramines but not all chlorine-containing organic compounds.
The CC concentration in a clean swimming pool should be very low (< 1ppm and very often near 0). Many CCs are further oxidized and destroyed by UV light and are pretty volatile compounds (they will naturally outgas from pool water),
It is possible to detect high levels of CCs temporarily in pool water, and the CC level will fluctuate from time to time. Still, any prolonged measure of CCs above 1ppm indicates a problem with the pool water being tested.
Water suffering from an algae bloom, being treated to destroy algae, or having had a high bather load will often generate high CCs while the free chlorine is disinfecting pathogens and oxidizing bather waste. Eventually, though, the CCs of a clean pool should be below 0.5 ppm most of the time.
What are Other Sources of Combined Chlorines in Pool Water?
Some chemical compounds, such as potassium monopersulfate (a standard non-chlorine shock used in hot tubs and sold in products like Oxibrite) or sulfamic acid (an organic acid used to remove calcium and metal scale) will show up on the chlorine tests as CCs.
Free Chlorine testing after using Sulfamic Acid is discussed in Acid#FC_Testing_After_Using_Sulfamic_Acid.
Potassium Monopersulfate Compounds, aka MPS or "non-chlorine shock' will interfere with the Combined Chlorine test.[2] Taylor Technolgies has the R-0867 Deox Reagent that will neutralize MPS effects on the CC test. R-0867 Deox Reagent is available in the K‑2041 (.75 oz) and K‑2042 (2 oz). It’s also available as a stand-alone kit, the K‑1518 FAS-DPD chlorine/monopersulfate test.
Why Do I Have Algae With a CC of 0?
CCs are a sign that nitrogen-based substances like ammonia or urea have reacted with chlorine and formed "combined chlorine." A certain amount of "free chlorine" is then needed to complete the oxidation process, which ends with nitrogen gas being released.
CCs are common in pools with a high bather load. They are usually more of a problem in public pools than in residential pools, especially when following the TFP protocol because there's always enough FC to quickly deal with the little CC that forms. Maybe after a big pool party, especially with little kids involved who have too much FOMO to go to the bathroom.
Plants like algae create chemicals like glucose from carbon dioxide and water. Using light, the carbon in carbon dioxide oxidizes the oxide into oxygen.[3]
6CO2 + 6H2O --> C6H12O6 + 6O2
Carbon dioxide + water--> glucose + oxygen.
This is how plants make oxygen and store energy in sugars. Most of the bulk of plants is carbon from carbon dioxide, and most of a tree's weight comes from the air.
The carbon in carbon dioxide is in the +4 state.
The carbon in glucose is 4 at 0, 1 at -1, and 1 at +1. The carbon is "reduced," which is the opposite of oxidized. Reduced just means that the oxidation state is lower or reduced because the atom gained negatively charged electrons.
When chlorine oxidizes the carbon in glucose back to a +4 oxidation state, it reverts to carbon dioxide.
This is similar to an animal using oxygen to burn sugars to release energy and exhale carbon dioxide.
So, chlorine reacting with algae is mostly an oxidation reaction, not a combination. Algae is converted chiefly back into carbon dioxide and water.
Chlorine can combine with carbon compounds, such as methane (CH4), by replacing the hydrogen ions.
Carbon in methane is in the -4 oxidation state.
Algae mainly does not create CCs.
CCs are created mainly by compounds like ammonia, where the nitrogen is in the -3 state. For ammonia, you get combination and oxidation. So, the CCs eventually go away, especially in sunlight, where UV photons knock loose electrons from the nitrogen and make it easier for the chlorine to take them.
Active chlorine is +1, so it bonds with more negatively charged atoms, like nitrogen in the -3 state or carbon in the -4 state.
The carbon in algae has a zero net charge.
So, the reaction of chlorine with algae is mostly oxidation and not a combination.
