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Many water and wastewater treatment plants have converted their disinfection method from gas chlorine to sodium hypochlorite. Regulatory agencies deem it safer than chlorine gas, and laws are proposed to replace chlorine installations with “inherently safer technology,” including sodium hypochlorite.

Despite its reputation as a safer disinfectant, sodium hypochlorite accidents occur.  Part of the reason is complacence because of the mistaken belief that sodium hypochlorite is harmless. After all, it’s just bleach, right?

Not really. Household bleach is about 5% sodium hypochlorite by volume, much more dilute than sodium hypochlorite used for treatment plant disinfection, which is 10 to 15%.

General Characteristics and Safety Concerns

Sodium hypochlorite is highly unstable, extremely corrosive, and exposure can cause extreme damage to the skin and eyes.
Personal protective equipment is a must when handling this chemical.

Sodium hypochlorite is also hard on storage containers and equipment, resulting in leaks, plugging and scaling that require caution during repair. Inspect the pipe connections, meters, fittings, and tanks frequently to resolve leaks as soon as possible.

Off-gassing caused by the degradation of sodium hypochlorite can bind pumps or rupture valves. After accepting a delivery, let the sodium hypochlorite sit a few hours to liberate some of the gas before it enters the pumping system.

The Chlorine Institute, Inc. provides excellent publications on sodium hypochlorite safety, including The Sodium Hypochlorite Manual and Safe Handling of Sodium Hypochlorite Video. Many of their manuals and pamphlets can be downloaded for free or you can pay to order a hard copy. Jones Chemical, Inc. has a link to the Sodium Hypochlorite Manual on their website as well. They have a number of other pamphlets and safety information on their site as well. 

Be sure to read the
Safety Data Sheet before handling sodium hypochlorite. (This one is from Kuehne Co., but your supplier should provide you with a copy).

Sodium Hypochlorite Incompatibility

One of the biggest dangers of working with sodium hypochlorite results from accidentally mixing it with incompatible materials.

Chlorine Institute has a free Sodium Hypochlorite Incompatibility Chart that lists 38 incompatible materials and what happens when they contact sodium hypochlorite. Results range from releasing chlorine gas to formation of explosive compounds.

The Chlorine Institute recommends installing signs on the sodium hypochlorite tanks, unloading lines and stickers on the piping stating:

Sodium Hypochlorite Only

Using the 
Sodium Hypochlorite Customers Generic Safety and Security Checklist is another step to prevent incompatible reactions that could harm employees or citizens.

Sodium Hypochlorite accidents:

City of Mollala, OR, 2009
Greenbrook Water Plant Explosion, Kitchener, ONT, 2014
Hypochlorite plus urea explosion
Holland Water Treatment Plant Experiences

Chemical Reaction Causes Respiratory Tract Irritation

Sodium Hypochlorite Safety