By Jack Brubaker Updated Mar 24, 2022
Both pool chlorine and household bleach rely on hypochlorite ions to perform their disinfecting and bleaching functions. However, the chlorine used in swimming pools is chemically and quantitatively much stronger than the sodium hypochlorite found in most household bleach products.
The primary active ingredient in commercial pool chlorine is calcium hypochlorite, Ca(OCl)₂. Some public or commercial pools may also use chlorine gas or chloramine formulations, but calcium hypochlorite remains the most common. Household bleach, by contrast, contains sodium hypochlorite, NaOCl.
Pool chlorine sold for swimming‑pool use typically contains about 65 percent active ingredient by weight. In comparison, household bleach generally holds only 5–6 percent sodium hypochlorite by weight.
When dissolved in water, both calcium hypochlorite and sodium hypochlorite release hypochlorite ions. Depending on the water’s pH, these ions can transform into hypochlorous acid (HOCl), the species most effective at oxidizing and killing microorganisms.
“Free available chlorine” (FAC) refers to the combined concentration of hypochlorite ions and hypochlorous acid present in a solution. FAC is the metric that truly reflects a water‑based solution’s disinfecting power.
Consider dissolving one gram of pool chlorine (65 % Ca(OCl)₂) in one liter of water. This yields an FAC level of 0.47 g L⁻¹. The same mass of household bleach (6 % NaOCl) in identical conditions produces only 0.04 g L⁻¹ of FAC.
In other words, gram‑for‑gram, pool chlorine delivers roughly eleven times the free available chlorine of household bleach.
