Titan Water Systems

Shock Chlorination

Alberta Agriculture & Rural Development

Shock chlorination is a relatively inexpensive and straightforward procedure used to control bacteria in water wells. Many types of bacteria can contaminate wells, but the most common are iron-related (IRB) and sulfate-reducing bacteria (SRB). Although not a cause of health problems in humans, these nuisance bacteria may coat the inside of the well casing, water piping and pumping equipment, creating problems such as:

Wells can also be contaminated with harmful bacteria such as fecal coliforms or E. coli. Shock chlorination is the most effective method to eliminate them. Bacteria may be introduced during drilling of a well or when pumps are removed for repair and laid on the ground. However, IRBs and SRBs (as well as other bacteria) can exist naturally in groundwater.

A well creates a direct path for oxygen to travel into the ground where it would not normally exist accelerating the growth of bacteria that require oxygen. When a well is pumped, the water flowing in will also bring in nutrients that enhance bacterial growth.


Shock chlorination is a process used in many swimming pools, water wells, springs, and other water sources to reduce the bacterial and algal residue in the water. Shock chlorination is performed by mixing a large amount of sodium hypochlorite, which can be in the form of a powder or a liquid such as chlorine bleach, into the water. Water that is being shock chlorinated should not be swum in or drunk until the sodium hypochlorite count in the water goes down to three ppm or less. Commercial sodium hypochlorite should not be mixed with commercial calcium hypochlorite, as there is a risk of explosion.