Why Swimming Pools Have Chlorine [Pool Chlorine Guide]
Chlorine manifests as the hero of the swimming pool world. It acts as a diligent protector, keeping the water safe and pristine for swimmers of all kinds.
But why do swimming pools need chlorine? What is the history of swimming pool chlorine use and what is the science behind it? Let’s dive deeper into the aqueous universe of chlorinated pools—and why exactly they have chlorine.
The science behind chlorine in pools
Chlorine works as a disinfectant by forming hypochlorous acid and the hypochlorite ion, which oxidise the bacteria in swimming pool water, effectively killing them.
The concentration of chlorine in the water determines how effectively it can kill germs. High chlorine levels mean the water is highly disinfected, but too high a concentration can be harmful to swimmers.
From a scientific point of view, chlorine is an efficient and cost-effective way to keep pool water sanitised. It is readily available and easily controlled, making it a popular choice for maintaining clean swimming pools. With its strong oxidising properties, chlorine can also protect against algae and other harmful microorganisms.
💡 Did You Know? That strong chlorine smell isn’t what you think…
Contrary to popular belief, a strong chlorine smell doesn’t always signify a high chlorine concentration. It’s actually the smell of chloramines or combined chlorine, compounds formed when chlorine reacts with organic matter, like sweat or urine. These compounds cause eye and skin irritation.
As the ideal level of combined chlorine in a pool should be around zero, when there’s too much combined chlorine in a pool, it usually means there’s not enough free chlorine to sanitise the water.
So, if you’re experiencing a strong chlorine smell while swimming, it may be time for the pool operator to adjust the levels.
Why swimming pool chlorine matters
As chlorine kills bacteria by oxidising them, it’s often considered the most effective form of pool disinfection.
In fact, according to the Centers for Disease Control and Prevention (CDC), disinfection with chlorine or bromine and pH is the first defence against the germs that cause swimming-related illnesses in pools, hot tubs/spas, and water playgrounds. This helps effectively prevent the spread of diseases like E. coli and Shigella.
Too high chlorine levels (over 1-3 ppm) can also cause health problems for swimmers, including skin and eye irritation. On the other hand, too low chlorine levels (below 1 ppm) can result in poor water quality, increasing the risk of illness.
But chlorine isn’t just a powerful germ killer; it also helps keep your pool free from algae. Algae can quickly take over a pool, turning the water green and making it unsafe for swimming. Chlorine prevents this by breaking down algae’s cell structure and inhibiting its growth.
Overall, chlorine plays a vital role in maintaining the health and safety of swimming pools. Without it, pools would quickly become breeding grounds for bacteria and unsanitary to swim in.
The Chlorine Chronicles: A historical perspective
The use of chlorine in swimming pools dates back over a century, with its primary purpose being to kill harmful bacteria and control algae growth.
Here’s a quick timeline of chlorine development to help you understand exactly why pools started using chlorine in the first place:
- 1774: Hydrochloric acid (HCl) was known to the alchemists, but the gaseous element of chlorine itself was first produced/discovered in 1774 by Carl Wilhelm Scheele (chemist) in Uppsala, Sweden. The name was given based on the Greek ‘chloros‘, meaning greenish yellow.
- 1807: Humphry Davy (chemist) investigated and finally concluded that it was not only a simple substance, but that it was truly an element.
- 1810: Announcement of chlorine as an element occurs and use of chlorine for its bleaching properties begins, yet it took another decade for some chemists finally to accept its elemental title as scientific fact.
- 1897: Chlorination for the disinfection of water supplies was first reported in England, where a ‘bleach solution’ was reportedly used to disinfect a water main in Maidstone, Kent, UK, after a typhoid outbreak. (Note: ‘bleach solution’ was a term used to describe these early chlorine products, do not add any bleach solution to your pool.)
- 1909: In the U.S, the first commercial delivery of liquefied chlorine in cylinders occurred. Additionally, a Michigan company was the first in America to ship liquid chlorine in a 15-ton tank carload.
- 1910: The first attempt to sterilise a pool with chlorine occurs in the United States, at Brown University by graduate student John Wymond Miller Bunker. Following the Brown University experiment, the Lancet began publishing papers regarding the bacterial contamination of swimming baths and methods of sterilisation, such as chlorination.
- 1910-1950: Regular use of chlorine for water and swimming sanitation begins.
- 1949: Recommended Practice for Design, Equipment and Operation of Swimming Pools and Other Public Bathing Places (1949 Edition) is updated, with key changes to standards for water chlorination — See image below.
- 1950: In the mid-20th century, chlorine compounds with cyanuric acid became available for pools. Like previous chlorine sterilisers, these compounds produce hypochlorous acid, an effective sanitizer.
- 1961: The United States Public Health Service first published a model ordinance governing the construction, sterilisation, and use of public pools, including more advanced chlorination for sanitation recommendations.
Recommended Practice for Design, Equipment and Operation of Swimming Pools and Other Public Bathing Places (1949 Edition)
Today, chlorine remains the go-to method for pool sanitisation, with advancements in technology making it safer and easier to use and automating the process of chlorination.
Pool managers like the Bayrol Pool Manager System even offer remote control and monitoring of pool chemical levels, ensuring that chlorine levels are always at their optimum for a safe swimming experience.
How to balance pool chlorine levels
Ensuring all pool chemicals and chlorine levels in your swimming pool water are balanced is essential. A high chlorine concentration can affect swimmers’ skin barrier, causing dryness and irritation, while low chlorine levels may not kill bacteria effectively. Regular water testing and dosing and proper maintenance can help maintain the ideal balance.
To reduce pool chlorine levels, here are some of our top tips:
- Use a DPD testing kit to help you test your pool for high or low chlorine levels.
- Use Blue Horizons Chlorine Reducer to help you reduce chlorine levels in your pool.
- Maintain proper pool hygiene, such as regularly brushing the walls and floor of your pool to remove any organic matter or debris that can react with chlorine.
- Ensure proper circulation and filtration of your pool water. This will help prevent algae growth and keep the water clean, reducing the need for excessive chlorine use.
- Take breaks from swimming in heavily chlorinated pools to give your skin and eyes a rest. Spending too much time in highly chlorinated water can cause irritation and dryness.
- Consider alternative sanitisation methods, such as using UV or ozone systems, which require less chlorine and are gentler on swimmers’ skin.
Alternatives to chlorine
While chlorine is highly effective, it has its downsides. That’s why there are alternatives like ozone systems to keep your pool clean. Despite their convenience, they may not be quite as effective as chlorine at killing bacteria, and as such, they are often used in conjunction with chlorinated systems.
A few alternatives could include:
- Saltwater pools use a salt chlorinator to produce chlorine from salt, eliminating the need for regular chlorine dosing. However, they still require some manual chlorine adjustments.
- UV sanitation involves using ultraviolet light to purify pool water. It’s effective in killing bacteria and has fewer side effects than chlorine but may not fully eliminate algae growth.
Types of pools and why they need chlorine
Outdoor pools and chlorine
Chlorinated water in outdoor pools can react with sunlight, causing the chlorine to dissipate more quickly. This means outdoor pools may need more frequent chlorination or stabilising agents to maintain suitable chlorine levels.
Indoor pools and chlorine
Indoor pools are typically more stable because they are not exposed to the elements. However, it’s essential to regularly test and monitor chlorine levels in indoor pools as well since they can accumulate chloramines (a byproduct of chlorine reacting with organic compounds).
Hot tubs and chlorine
Even as a smaller body of water, balanced hot tub chlorine levels are crucial to keep the water clean and safe. The higher temperatures in hot tubs can also speed up the breakdown of chlorine, so it’s crucial to check and adjust chlorine levels more frequently.
Closing thoughts
Overall, regardless of the type of pool or spa, chlorine is an essential component in maintaining a healthy swimming environment. As long as the chlorine levels in the pool are adequately maintained, swimming in a chlorinated pool should be a safe and enjoyable experience.
At Blue Cube Pools, we understand the importance of proper pool maintenance and balancing chlorine levels. Our range of high-quality products, including DPD testing kit and Blue Horizons Chlorine Reducer, can help you keep your pool safe and inviting for all swimmers.
Alternatively, have one of our expert pool engineers take care of all your pool maintenance needs with our affordable swimming pool maintenance and water treatment services. So, sit back, relax, and enjoy a clean, safe swim in your chlorine-treated pool!
Contact us today for more information or support with your pool dosing and testing!
