Byproducts of Calcium Hypochlorite Pool Disinfection

calcium hypochlorite
Calcium hypochlorite is a commonly used disinfectant in pool water treatment, effectively eliminating bacteria, algae, and other contaminants.

The Role of Calcium Hypochlorite in Pool Disinfection

Formation of Byproducts

Despite its effectiveness in disinfection, the use of calcium hypochlorite can lead to the formation of byproducts through various chemical reactions. These byproducts may include chloramines, trihalomethanes (THMs), haloacetic acids (HAAs), and other disinfection byproducts (DBPs).


Chloramines are formed when HOCl reacts with ammonia and organic nitrogen compounds present in pool water, typically introduced through sweat, urine, and other bodily fluids from swimmers. Chloramines contribute to the characteristic “chlorine smell” in pools and can cause eye and skin irritation in swimmers.

Trihalomethanes (THMs) and Haloacetic Acids (HAAs)

THMs and HAAs are formed when HOCl reacts with organic matter in pool water, such as leaves, algae, and other debris. These disinfection byproducts are classified as potential carcinogens and are regulated by health agencies due to their long-term health risks.

Implications for Water Quality and Swimmer Health

The presence of disinfection byproducts in pool water can have several implications for water quality and swimmer health:

Irritation: Chloramines, THMs, and HAAs can cause irritation to the eyes, skin, and respiratory system in swimmers, leading to discomfort and potential health issues.

Odor: The presence of chloramines contributes to the characteristic “chlorine smell” associated with poorly maintained pools, which can be unpleasant for swimmers and indicate inadequate sanitation.

Long-term Health Risks: Exposure to THMs and HAAs over extended periods may increase the risk of certain health problems, including cancer and reproductive issues, prompting regulatory agencies to establish guidelines for their maximum allowable concentrations in pool water.

Mitigation Strategies

Proper Filtration and Circulation: Adequate filtration and circulation systems help remove organic and inorganic contaminants from pool water, reducing the precursor compounds that contribute to byproduct formation.

Maintaining Proper pH and Free Chlorine Levels: Maintaining the pH of pool water within the recommended range (7.2-7.6) and ensuring adequate free chlorine levels help optimize the effectiveness of calcium hypochlorite disinfection and minimize the formation of byproducts.

Supplemental Oxidation: Using supplemental oxidants such as potassium monopersulfate or non-chlorine shock treatments can help break down organic contaminants and reduce the formation of chloramines and other disinfection byproducts.