How to use sodium hypochlorite to clean your pool

Sodium hypochlorite is one of the best options for pool cleaning. Sometimes called “liquid chlorine” or “liquid bleach,” this chemical sanitizes pool water in the following ways:

• Kills bacteria and pathogens
• Kills algae and prevents future growth
• Oxidizes non-living pool contaminants (such as human body fluids)
• Leaves a reservoir of chlorine in pool water to help keep it clean

In this guide, we’ll explain how sodium hypochlorite works, how to use it, and make note of a few cautions and considerations regarding its use and storage.

Sodium Hypochlorite Quick Facts

Chemical formula: NaOCl

• Other names: liquid bleach, liquid chlorine
• Use: household bleach (1.5-6%) or pool sanitizer (10-12.5%)
• Action: kills bacteria, oxidizes contaminants, super-chlorinates pool water
• Appearance: clear, yellow liquid
• Odor: chlorine
• pH: 11-13

What is sodium hypochlorite?

Sodium hypochlorite, or NaOCl, is an aqueous solution commonly known as liquid chlorine or household bleach. It is manufactured by mixing chlorine gas in solution of sodium hydroxide (NaOH).

At concentrations ranging from 1.5-6%, sodium hypochlorite is used as household bleach for cleaning and laundry. At concentrations ranging from 10-12.5%, it is appropriate for cleaning private or commercial pool systems.

How does sodium hypochlorite work?

In aqueous solution, sodium hypochlorite forms hypochlorous acid, HOCl, a weak acid. Hypochlorous acid dissociates to form the negatively charged hypochlorite ion, or OCl-. Hypochlorous acid and the hypochlorite ion exist in equilibrium according to the equation:

HOCl + H2O <-> OCl- + H3O+

The pKa, or acid dissociation constant, of NaOCl is about 7.5. The equilibrium is shifted left or right depending on the pH of the pool water. At a pH of 7.5, the two species will be equal in concentration. That means that half the chlorine will exist as hypochlorous acid, and the other half will exist in the form of hypochlorite, OCl-.

Sodium hypochlorite effectively works as an anti-microbial and oxidizing agent. HOCl destroys pathogenic organisms by entering the cell and disrupting vital proteins. It simultaneously works on non-living contaminants, including human waste products and ammonia, via its strong oxidizing properties.

Instructions for using 12.5% sodium hypochlorite

Sodium hypochlorite can be added to the pool manually or using an automatic pump. A pump is preferred because it circumvents the need for direct handling of chemicals, but is not necessary. Sodium hypochlorite should be added on the deep end of the pool, observing all cautions (listed below), and following the instructions detailed by the pool manufacturer.

It is necessary to also secure the appropriate chemical testing equipment, to ensure that the chemical levels and pH of the pool water are within the acceptable range. The target pH of the pool is slightly alkaline at about pH7.5. Target levels of free chlorine are generally recommended to be in the range of 1-3ppm.

The addition of 10.6 fl. Oz. of sodium hypochlorite per 10,000 gallons of pool water will result in about 1ppm of free chlorine.

Cautions for 12.5% sodium hypochlorite

Sodium hypochlorite is a corrosive chemical, so precautions must be taken regarding handling and storage. Always observe the following precautions when using 12.5% sodium hypochlorite:

• Always use personal protective gear, including gloves and goggles or a face-shield, when handling 12.5% sodium hypochlorite
• Do not allow undiluted 12.5% sodium hypochlorite to come into contact with metal parts of the swimming pool, such as railings and ladders.
• Pour 12.5% sodium hypochlorite slowly and carefully to avoid backsplash of undiluted chemical.
• If you are using a pump to add sodium hypochlorite, be sure that the port is set up according to the manufacturer’s instructions. This should ensure that undiluted sodium hypochlorite will not come into contact with metal parts.
• Free chlorine levels must be kept in the range of 1-3ppm for safe bathing.

How to store sodium hypochlorite

Over time, sodium hypochlorite degrades to form sodium chloride and water. Users are encouraged to purchase sodium chlorite in smaller batches to ensure freshness and efficacy.

Maintaining appropriate storage conditions can help extend the useful shelf-life of sodium hypochlorite. Sunlight and high-temperature should be avoided, since they will speed up the rate of degradation.

Sodium hypochlorite must be stored in a cool and ventilated area for safety reasons.

Where to buy sodium hypochlorite

As a matter of safety, it is critical to buy high-quality sodium hypochlorite for pool cleaning. Lab Alley is pleased to provide you with premium 12.5% sodium hypochlorite that is even suitable for drinking water treatment.

If you have additional questions regarding 12.5% sodium hypochlorite, or any of our products, please feel free to contact us for more information.