At What Temperature Does Chlorine Evaporate from Water?

Chemical element chlorine is frequently employed in water treatment procedures as a disinfectant. Bacteria, viruses, and other germs that might lead to illnesses and infections are eliminated by chlorine. Chlorine does, however, have several disadvantages, including a disagreeable taste and odour, the tendency to react with organic materials and produce dangerous byproducts, and detrimental effects on aquatic life.

Letting the chlorine naturally evaporate is one method of getting rid of it from water. Chlorine is a volatile chemical that, under certain circumstances, can leak from water into the atmosphere. In this blog we will discuss At What Temperature Does Chlorine Evaporate from Water?

Quick Summary

  • Chlorine, mostly in the form of free chlorine, a volatile compound, can evaporate from water.
  • Temperature, surface area, and the presence of additional chemicals all affect how long something will take to evaporate.
  • Chlorine can partially evaporate in open containers in a few hours to days, but it takes longer for chlorine to completely vaporise.
  • Faster chlorine evaporation from water is made possible by warmer temperatures.
  • In comparison to cold water, chlorine evaporates more quickly in hot water.
  • Boiling the water, using an aerator, or using a dechlorinator will hasten the evaporation of chlorine.
  • Chlorine is useful for disinfection but has downsides such an unpleasant taste and odour and the potential to destroy aquatic life.

How Does Chlorine Evaporate from Water?

Depending on the pH, temperature, and other conditions, chlorine can be found in water in a variety of forms. Chlorine in water often takes the following forms:

  • When chlorine gas, sodium hypochlorite (bleach), or calcium hypochlorite (bleach powder) are added to water, hypochlorous acid (HOCl) and hypochlorite ion (OCl-), which are created as a result, are combined to form free chlorine. The most effective type of chlorine for disinfection is free chlorine since it can quickly penetrate and kill bacteria’ cell walls.
  • Chlorine that has been combined is produced when free chlorine interacts with organic materials like ammonia, nitrogen compounds, or humic substances. Combining chlorine results in chloramines, which have lower disinfection efficacy and are more prone to impart disagreeable tastes and odours to water. Additionally, combined chlorine takes longer to disappear from water since it has a longer half-life than free chlorine.
  • The sum of combined and free chlorine in water is the total chlorine content.

As free chlorine is the most volatile type of chlorine, it is mostly mentioned when we discuss chlorine evaporation from water. Depending on the circumstances, free chlorine can evaporate from water if left motionless for 1–5 days. The following variables influence the rate of chlorine evaporation:

  • Temperature: Evaporation happens more quickly at higher temperatures. Heat makes molecules more likely to escape from the liquid phase into the gas phase by increasing their kinetic energy. It can take up to 24 hours for chlorine to evaporate from water while it’s at room temperature (68 °F or 20 °C). Chlorine can evaporate from water in as little as a few minutes at boiling point (212 °F or 100 °C).
  • Surface area: Evaporation happens more quickly the larger the surface area. More molecules are exposed to the air and have a greater possibility of escaping as a result. A small tray of water, as an illustration, will lose chlorine more quickly than a deep glass of water.
  • Air movement: Evaporation happens more quickly the more air that is moving. This is so that evaporated molecules can be removed from the atmosphere and a concentration gradient that encourages further evaporation can be created. For instance, positioning a fan close to the water container will hasten the evaporation of chlorine.
  • pH level: Evaporation happens more quickly the lower the pH level. This is so because hypochlorous acid (HOCl), which is more volatile than hypochlorite ion (OCl-), forms more readily at lower pH values. For instance, adding vinegar or lemon juice to the water will increase the amount of free chlorine while lowering the pH.

How to Speed Up Chlorine Evaporation from Water?

You can utilise a few straightforward techniques that benefit from the aforementioned elements if you want to swiftly remove chlorine from your tap water. The following advice will help you hasten chlorine’s evaporation from water:

  • Boil the water: Since boiling raises the water’s temperature and surface area, it is the most efficient approach to remove chlorine. Any leftover bacteria in the water are also destroyed by boiling. Boiling uses a lot of energy, though, and it also has the potential to change some of the minerals and nutrients in the water.
  • Aerator: Use an aerator to add tiny bubbles to the water stream. An aerator is a device that you can attach to your faucet to do this. This increases the water’s surface area and airflow, which raises its oxygen content and lowers its chlorine concentration. Aerators are cheap, simple to operate, and to install.
  • Use a filter: A filter is a device that purges water of impurities by forcing the water through a porous substance that captures or absorbs them. Chlorine can be removed from water using a variety of filters, including reverse osmosis, distillation, and activated carbon filters. Other contaminants like sediment, metals, or pesticides can also be eliminated from water through filters. However, filters also need routine upkeep and replacement, and they could also take some of the water’s essential minerals and nutrients with them.
  • Use a dechlorinator: A dechlorinator is a chemical that reacts with chlorine in water to produce harmless chemicals, neutralising the chlorine. Dechlorinators of various kinds, such as sodium thiosulfate, sodium sulfite, or ascorbic acid, are available to remove chlorine from water. To prevent chlorine toxicity for the fish and plants in aquariums and swimming pools, dechlorinators are frequently utilised. Dechlorinators, however, have the potential to introduce some undesired residues or byproducts as well as change the pH and hardness of the water.

What are the Benefits and Drawbacks of Chlorine in Water?

Although chlorine is a common disinfectant used in water treatment procedures, it also has several advantages and disadvantages that have an impact on the water’s quality and safety. The benefits and drawbacks of chlorine in water are as follows:

Chlorine in Water Benefits

  • Harms hazardous microbes: Typhoid, cholera, dysentery, and giardiasis are a few examples of waterborne diseases that can be caused by bacteria, viruses, parasites, and other microbes that can be killed or inactivated by chlorine. Additionally, chlorine can stop the development of biofilms, slime, mould, and algae that can contaminate water sources and distribution networks.
  • Reduces undesirable tastes and odours: Organic matter, iron, manganese, hydrogen sulphide, and other substances may cause water to have unpleasant tastes and aromas that chlorine can assist to eliminate or lessen. Chlorine may make water more clear and sparkly, which can enhance its visual appeal.

Drawbacks of Chlorine in Water

  • Disinfection by-products (DBPs), such as trihalomethanes (THMs) and haloacetic acids (HAAs), are produced when chlorine reacts with organic materials and other elements in water. These DBPs have been connected to higher cancer risks, issues with reproduction, liver damage, and other negative health impacts.
  • Chlorine can irritate the skin, hair, eyes, and respiratory system in those who are sensitive to it or allergic to it. It can also induce dryness. Chlorine can also discolour clothes, dry out the skin and hair, and harm rubber appliance seals.
  • Chlorine can change the acidity and mineral content of water, which can change both the pH and hardness of the water. This may have an impact on how easily pipes and fixtures corrode, how easily metals dissolve, and how well soap and detergent work.


Although chlorine is a common disinfectant used in water treatment procedures, it also has several downsides that some people feel should be eliminated from tap water.

Natural evaporation of chlorine from water is possible, although the speed of evaporation is influenced by a number of variables, including temperature, surface area, air circulation, and pH level. Boiling, aerating, filtering, or dechlorinating are some processes that can hasten the evaporation of chlorine from water.

However, each approach has advantages and disadvantages of its own and may have a varied impact on the water’s quality and flavour. Therefore, it’s critical to consider both the advantages and disadvantages of each approach before deciding which one best satisfies your requirements and preferences.


Can chlorine evaporate from water?

Chlorine does indeed evaporatively leave water. It is a volatile substance that may change from a liquid state in water to a gaseous state in the air given the correct circumstances.

How long does it take for chlorine to evaporate out of water?

Temperature, surface area, and the presence of other chemicals are some of the variables that might affect how long it takes chlorine to evaporate from water. Typically, a significant part of chlorine can evaporate in open containers exposed to air in a matter of hours to days. Complete evaporation, however, can take more time.

Does chlorine evaporate in the heat?

Yes, in warmer environments, chlorine can evaporate more easily. Chlorine evaporation is accelerated by higher temperatures because they give water molecules more energy. It is important to keep in mind, though, that the rate of evaporation is also influenced by other elements, including humidity, airflow, and the amount of chlorine in the water.

Does chlorine evaporate faster in hot water? 

Yes, compared to cold water, chlorine tends to evaporate more quickly in hot water. The kinetic energy of the chlorine molecules grows as the water temperature rises, increasing the rate of evaporation. For its intended use, like as disinfection in swimming pools or water filtration systems, it is crucial to maintain the right quantity of chlorine in treated water.






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