Water Well Disinfection Calculator: WellChlor

Shock chlorination is a remedial or preventative strategy to disinfect water wells or distribution systems in order to control or prevent the growth of unacceptable levels of micro-organisms. When chlorination is properly conducted, the entire well casing, pump, distribution plumbing, and some water system equipment should be disinfected.

The biocidal effects of chlorine are most effective at pH levels of 5.5 to 6.5. However the addition of chlorine raises the pH of water. To buffer this effect during the disinfection process, a weak acid like vinegar (i.e. 5% acetic acid) can be added to the water in the mixing tank to reduce the pH. The addition of chlorine will raise the pH in the final mixing solution to the range needed for optimal disinfection.

This calculator incorporates a pH adjustment to calculate the volumes of chlorine and vinegar necessary for optimal disinfection.

Please note that if you are unsure of the disinfection process it is recommended that you use a registered well driller and/or pump installer to carry out the work.

Before you begin, please read the following:

• Water Well Chlorination using pH Adjustment and the "WellChlor" Calculator (PDF)
  This document describes the disinfection process for both large diameter bored wells and small diameter drilled wells, the recommended safety procedures and the bacterial testing required after disinfection.

Please choose the appropriate calculator:

• WellChlor for Small Diameter Drilled Wells
  This calculator calculates the volumes of chlorine product, vinegar and water to be added to an external mixing tank. The water volume is based on adding a water volume equal to twice the volume of water in the well.
• WellChlor for Large Diameter Bored Wells
  This calculator calculates the volumes of chlorine product and vinegar to be mixed into the existing column of water in the well. The large volume of water in most bored wells precludes the practical use of an external mixing tank.