Trichlor or Cal Hypo?

Trichlor or Cal Hypo?


The choice of sanitizer can significantly impact the costs of operating a large aquatics facility. This article addresses potential costs associated with two commonly used sanitizers: Calcium Hypochlorite (or Cal Hypo) and Trichloroisocyanuric Acid (or Trichlor).

When Calcium Hypochlorite and Trichloroisocyanuric Acid are added to pool water, they clearly increase available chlorine, however they also affect pH, alkalinity and either calcium hardness or cyanuric acid levels.

Think of it this way: Every time these sanitizers are added to the water, they bring additional chemicals “inside” them as well. Sometimes these “extra” chemicals are beneficial, sometimes you will have to pay to get rid of them.

Calcium Hypochlorite (Cal Hypo)

Calcium hardness plays a vital role in water chemistry, helping protect plaster, concrete and metal objects from corrosion caused by aggressive water.

A minimum of 150 ppm CH is required for pool water,   For plaster pools, AquaClear Engineer recommends a CH of at least 200 ppm. When the water falls between 150 and 1,000 ppm of CH, the saturation index can be maintained to prevent scale and cloudy water formation.

Adding 10 ppm of available chlorine using calcium hypochlorite will add 8 ppm CH, according to APSP. For a pool starting at 150 ppm CH, adding 10 ppm available chlorine daily with cal hypo would cause the CH in the pool water to reach 1,006 ppm in 107 days.

When water reaches 1,000 ppm CH, removing and replacing 1% will drop the CH 8 ppm, if the source water is 200 ppm CH. In a 100,000-gallon pool, the replacement amount equals 1,000 gallons. This will counter the CH added by the daily dose of cal hypo at these concentrations and rates.


Trichloroisocyanuric Acid (TCCA, Trichlor)

Cyanuric Acid (CYA) helps protect the available chlorine from decomposition caused by UV light.

A maximum of 100 ppm CYA is recommended by AquaClear Engineer, while the Model Aquatic Health Code recommends a maximum of 90 ppm CYA. For indoor pools, CYA is considered unnecessary and is not recommended, according to AquaClear Engineers.

Adding 10 ppm of available chlorine using trichlor will raise CYA by 6 ppm, according to APSP. For a pool starting at 30 ppm CYA, using trichlor to add 10 ppm of available chlorine each day would cause the CYA to reach 90 ppm in 10 days and 102 ppm in 12 days.

When CYA levels reach 90 ppm, 6.7% of the water volume must be removed and replaced to counter this daily addition of trichlor. At 100 ppm CYA, removing and replacing 6.0% of the water will counter the CYA added daily by the use of trichlor. For a 100,000-gallon pool, that amounts to 6,700 gallons and 6,000 gallons respectively.


By comparing the costs of using Calcium Hypochlorite (Cal Hypo) with those of using Trichloroisocyanuric Acid (TCCA,Trichlor),As for the use of Calcium Hypochlorite, cal hypo boosts pH, alkalinity and calcium hardness (CH) levels. Trichlor has the opposite effect on pH and alkalinity — reducing it. And where cal hypo affects CH, trichlor increases cyanuric acid (CYA). an estimate was made based on 2020 water and sewage rates in China, combined with 2020 chemical costs. This estimate shows that costs incurred by facilities using Cal Hypo might be considerably a little bit lower than those for the same facility using Trichlor. Both of them are high quality and efficient disinectant for a pool sanitation and maintenance.

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