Before discussing the proper way to store sodium hypochlorite, it is important to first understand how the quality of the sodium hypochlorite affects its storage life. For more information about sodium hypochlorite quality and how it affects the rate of decomposition, see Sodium Hypochlorite Decomposition.

Light, heat, organic matter, and certain heavy metals (such as copper, nickel, and cobalt) accelerate the rate of decomposition of sodium hypochlorite. The presence of transition metal ions (copper and nickel) is known to catalyze the decomposition of liquid sodium hypochlorite, contributing to the loss of sodium hypochlorite strength and the formation of oxygen. Loss of sodium hypochlorite strength means more product will be needed when the sodium hypochlorite is used as a disinfectant.

Oxygen build-up can pose problems when storing sodium hypochlorite in storage containers or sodium hypochlorite transport piping due to pressure build-up. By removing suspended solids to nearly undetectable levels from the sodium hypochlorite solution, the rate of decomposition is significantly reduced. In addition, the formation of oxygen is nearly eliminated.

All sodium hypochlorite decomposition is dependant on temperature. For any given temperature, the higher the strength, the faster it decomposes. In summary, for every 10⁰ C increase in storage temperature, the sodium hypochlorite will decompose at an increased rate factor of approximately 3.5.

Temperature

Storage of sodium hypochlorite at approximately 60°F (15° C) will greatly reduce the decomposition of the sodium hypochlorite. Therefore, if sodium hypochlorite decomposition is a problem in storage and shipping, in many cases the problem can be solved by cooling the stored sodium hypochlorite before shipping, and if necessary cooling it upon receipt at the distribution center.

At the production facility it is relatively easy to chill the sodium hypochlorite with a chilled water system and plate and frame heat exchangers. However, at the customer’s site or distribution location, it is usually easier to install the storage tanks, transport tote tanks, drums and bottles in a well insulated room or building and install air conditioning to cool the room.

If the time from production to receipt at the final site is kept to a minimum, it is common to not chill the sodium hypochlorite during the storage at the production site and during shipping, but to keep the sodium hypochlorite in an air conditioned room after receipt. In order to determine your best option, each application has to be reviewed based on sodium hypochlorite strength, storage temperature, and storage time.

Storage Tanks

Many different types of materials are used for construction of storage tanks for sodium hypochlorite. Two main types of the materials used are linear and crosslinked polyethylene and fiberglass reinforced plastic (FRP). Other choices include chlorobutyl rubber lined steel and titanium. In some countries where these materials are not readily available or the manufacturing quality is suspect, cubical concrete tanks lined with flexible plastic liners such as PVC have been successfully used. The choice of materials depends on available capital, tank location, and required service life. Some tanks may only last 3-5 years. If properly specified and maintained, the tanks could last 10-15 years. The only material noted for over 30 years service life is titanium.

For more information, see the Powell Sodium Hypochlorite General Information Handbook.

For more information about Determining the Strength of Sodium Hypochlorite, see "How to Determine the Strength of Sodium Hypochlorite."

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