How Much Chlorine To Add To Pool? Understanding Free Chlorine Vs Total Chlorine

Chlorine is one of the most affordable and widely used sanitizers for swimming pools and spas. It’s highly effective that’s why most people prefer it. Chlorine levels in the pool should be tested daily-at least-to ensure there is correct disinfection. Regular chlorination will ensure all harmful bacteria that pose some health problems in humans are eliminated. By learning how to test your water properly, you will be able to know the chlorine residual and requirement in your swimming pool water. If your pool gets a lot of traffic, you may have to test the chlorine levels more often.

How much chlorine to add to pool?

Most first time swimming pool owners often ask “how much chlorine should I add to my swimming pool?” To identify the amount of chlorine your swimming pool needs, you should consider several factors apart from your pool size alone. These factors help in determining how effective the chlorine added will be to your pool water. Let’s discuss some of the factors here.

The surface area and volume of the swimming pool

The surface area and volume of your swimming area directly affect the amount of chlorine you should add to your swimming pool. Swimming pools that have higher volumes of water contain higher amounts of contaminants. In addition, a pool with a bigger surface area also means there is higher evaporation of pool water and the dissolved chlorine. So the bigger the volume and surface area the higher the amount of chlorine needed.

Water temperature of your swimming pool

Temperature usually affects the needed amount of chlorine in your pool in different ways. If your pool water is warm, you may require more amounts of chlorine.

Subjection to sunlight

When unstabilized chlorine is exposed to the sun’s rays, thus easily evaporates when it comes into direct contact with the sun’s rays. Actually, sunlight may destroy almost all the chlorine in a swimming pool in a matter of hours. This means that if your swimming pool receives a lot of direct exposure to the sunlight, you may require more chlorine.

Amount of cyanuric acid

Cyanuric acid (stabilizer), decreases the elimination of chlorine by the sun’s rays especially in outdoor swimming pools.

If you use any stabilizer in your swimming pool, then you should add chlorine to your swimming pool often so that you can keep the right amount of ppm concentration.
When buying a stabilizer, you can get one that is premixed with chlorine. If you chlorinate you swimming pool daily, then stabilized chlorine is best. You can also buy unstabilized chlorine and stabilizer separately. This is best when you want to shock the swimming pool and then stabilize it later.

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Understanding free chlorine vs total chlorine in pools

Pool owners often get confused by the various types of chlorine present in the pool and this makes then uncertain on the type of chlorine to test for in the swimming pool. Your swimming pool water typically contains three different types of chlorine. Namely:
• Free chlorine(FC)
• Combined chlorine(CC)
• Total chlorine(TC)
To understand the difference between all these types, here are some explanations.

Free available chlorine (FAC) or (FC).

Free available chlorine or Free chlorine is often the determinant of the chlorines ability to disinfect your pool water. This is the reading of the levels of concentration of hypochlorite ion and hydrochlorous acid in the pool water in ppm (parts per million).
Hypochlorous acid is formed when a chlorine compound dissolves in water. Hypochlorous acid is the usually the functional disinfectant form of chlorine in your pool water.
In short Free Chlorine is the part of chlorinated water that has not reacted with any contaminants in the water and can help in killing bacteria and any other contaminants in the water.
When the PH is 6.0, a bit of the Hypochlrous acid starts changing into the hypochlorite ion, then forms again to Hypochlorous acid. Hypochlrotie acid is a functional disinfectant type of chlorine, but it’s not as strong as Hypochlorous acid. To keep the chlorine as active as possible, it’s vital to maintain a pH range of 7.2 to 7.8.
To maintain pool water at an ideal quality, the Free Chlorine (FC) should be between 1.0 and 3.0 parts per million (ppm). You can test for Free Chlorine using DPD test kits and test strip. However, OTO kits will not work.

Combined available chlorine (CC)

When chlorine comes into contact with ammonia and nitrogen compounds in water such as urine, sweat, they react to form nitrogen and chloramines. Chloramines result into bad chlorine odor and cause irritation of the eyes to swimmers.

Chloramines are what is referred to as combined chlorine (CC). Combined chlorine is not as active in killing bacteria when compared to hypochlorite ion and hypochlorous acid. Combined chlorine can easily be changed to nitrogen and water through a process known as breakpoint chlorination.


Total chlorine (TC)

Total chlorine is simply a measure of combined chlorine and free available chlorine. This is the sum of the two types of chlorines in your swimming pools. The total chlorine should not be less than the free chlorine level.

Types of chlorines that are commonly used in pools

Swimming pools are often treated with sodium hypochlorite, lithium hypochlorite, chlorine gas and calcium hypochlorite. When either of these compounds gets into contact with water, they free HOCI (hypochlorous acid), an active sanitizing agent. One can add a stabilizer alone to help decrease the loss of chlorine in the pool water as a result of the sun’s rays.
After you have established how much chlorine is in the water, you can add approximately 10 times of the amount of free chlorine to eliminate it. The overdosing also known as super chlorination is the breakpoint chlorination.

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