From this question we know that what swimming pool stores refer to as "liquid chlorine" (sold in 10 gallon jugs) is most likely sodium hypochlorite ($\ce{NaOCl}$). In the spirit of Least Publishable Units (LPUs) I'll ask a brief sequel separate from the first question.

The worst is when microorganisms (algae) overrun the pool. In the presence of summer heat, ample sunlight, and perhaps some nutrients (just phosphates?), the green population can multiply rapidly. Is calcium hypochlorite ($\ce{Ca(ClO)2}$) (sold in crystal form) as effective as sodium hypochlorite ($\ce{NaOCl}$) in sanitizing a swimming pool from algae?


A certain talented fictional chemistry teacher whose fame rests on illicit activities apparently had little difficulty maintaining good water quality in his swimming pool. Yet anyone who has tried will attest that maintaining immaculate water clarity is sometimes a nontrivial objective.

This is the second in what may be a series of questions trying to understand the basics of maintaining a swimming pool. A quick search online will show an enormous number of results—all amateurish and none technical, hence the need for learned opinion.


1 Answer 1


Yim et al. [1] studied the effectiveness of various hypochlorite salt treatments against a particular strain of bacterial cells and Speers. They found that calcium hypochlorite was much more effective than sodium hypochlorite... but it should he used with care because if its high corrosivity:

Although HTH [calcium hypochlorite] is effective for decontaminating these B. anthracis strains, it is considered extremely corrosive to metals, skin and mucous membranes, eyes, and respiratory and gastrointestinal tract [2]. Therefore, to avoid material corrosion or toxicity, alternative disinfectants with high efficacy are needed.


  1. Jin-Hyeok Yim, Kwang-Young Song, Hyunsook Kim, Dongryeoul Bae, Jung-Whan Kun-Ho Seo (2021). "Effectiveness of calcium hypochlorite, quaternary ammonium compounds, and sodium hypochlorite in eliminating vegetative cells and spores of Bacillus anthracis surrogate". J Vet Sci. 2021 Jan; 22(1): e11. Published online 2021 Jan 18. https://doi.org/10.4142/jvs.2021.22.e11 PMCID: PMC7850788 PMID: 33522163

  2. Rogers JV, Ducatte GR, Choi YW, Early PC (2006). A preliminary assessment of Bacillus anthracis spore inactivation using an electrochemically activated solution (ECASOL) Lett Appl Microbiol. 2006; 43:482–488.


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