What is Total Alkalinity?



Total alkalinity is a measure of the total amount of dissolved particles in the water whose pH is higher than 7.0. For this definition, a particle is any object that does not break down completely when dissolved in water. Examples of particles include dirt, sand, and baking soda. Baking soda, unlike soda ash, does not break down completely, but instead remains as a compound and stays in the water for an extended period of time. Alkaline particles in pool water, at certain levels, act as a buffer to prevent rapid changes in the pool's pH. Thus, when the total alkalinity of the pool water is within the ideal levels, the pH of the water will tend to stay balanced for longer periods of time.


Alkalinity: See "Base If in section above.

Buffer: A buffer is a substance, which prevents rapid and large changes, usually in the pH of the environment it is LT}. In this case, the alkalinity of the water itself helps to minimize rapid changes in the pH of the water when reasonable amounts of acid are added.


The Total Alkalinity Scale

Total alkalinity is-measured in parts per million (ppm). The scale by which it is measured begins at zero ppm and has no upper limit. Generally, the maximum level concerning swimming pool users is on the order of 200 ppm, but the recommended ideal levels fall well below this amount.

Ideal Levels

The ideal level for total alkalinity varies with the type of surface the pool possesses. For all pool surfaces, the recommended level falls between 120 and 140 ppm if any trichlor, gas, or liquid chlorine, or bromine tablets or sticks are used, and 100-120 is dichlor, liquid chlorine, calcium-or lithium-hypochlorite is used.

* * Paradise recommends 120 ppm's of alkalinity, no matter what form of chlorine is used.

Time And Frequency Of Testing

Unlike chlorine and pH, total alkalinity does not need to be tested on a daily basis, due to the fact that it does not change rapidly. It is generally recommended to test the total alkalinity 2 to 4 times per month throughout the year. However, if the pool's pH is not remaining balanced, or large amounts of acid, soda ash or baking soda have been added to the pool, it is advisable to have the total alkalinity tested as soon as possible. There is no specific time of day at which the alkalinity should be tested but, again, for convenience, it is recommended that it be tested at the same time as the chlorine and pH tests.


Citrus Plants

As mentioned earlier, citrus plants contain a powerful acid called citric acid. Once this acid is introduced to the pool water, it lowers the pH, frequently to a large degree. In some cases, the amount of citric acid added to the water in this way is severe. In this case, it is advisable to keep as many leaves and citrus fruits out of the pool water as possible, whether by eliminating or relocating the plant, or by adding a cover to the pool.


In urban areas where a significant amount of air pollution exists, the rain, which falls, brings with it a significant amount of sulfuric acid. The pH of the rainwater in our area has been measured as low as 4.0, and this level is easily enough to lower the pH of the swimming pool an appreciable amount. It is important to test the pH as soon as possible after a rainstorm to ensure that it does not remain below ideal levels for an extended period of time.

Dirt And Debris

Some soils, especially those in the dry land area, are very alkaline. Since alkaline substances neutralize acid and raise the pH of water, the presence of large amounts of dirt and debris in the swimming pool can increase the pH significantly. In cases where large amounts of dirt and debris are entering the pool water, it is advisable to keep the pool covered as much as possible.

Pool Surface

The type of surface used on a swimming pool can also affect the pH of the pool water. Plaster or plaster based pool surfaces such as Pebble Tee, are porous, alkaline materials. They can absorb and neutralize acid in pool water, thereby raising its pH. In this case, small amounts of acid are generally needed to maintain a proper pH balance. Fiberglass, vinyl, and painted plaster pools, on the other hand, do not have porous surfaces, and thus do not absorb or neutralize acid in the water. Here, small amounts of soda ash or baking soda may be needed to keep the pH at a proper level after acid is added in the form of rain, citrus leaves, etc.

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