Water should be treated using Calcium Hypochlorite 60-70% or Sodium Hypochlorite 12.5 %, which can be purchased at swimming pool shops.

The initial dose to treat the contamination should be 7 grams of Calcium Hypochlorite or 40 ml of Sodium Hypochlorite (as used in swimming pools) per 1,000 litres of water in the tank at the time of treatment.  The water should be stirred then left to stand for at least 24 hours to allow the chlorine taste and smell to dissipate.  This dosage will disinfect the tank by bringing the Chlorine up to 5ppm.

To maintain a safe water supply after the initial dosage, 1 gram of Calcium Hypochlorite or 4 ml of Sodium Hypochlorite per 1,000 litres should be added to the tank weekly (this brings the chlorine level up to 0.7 ppm) and left to stand for a minimum of two hours.

It is important to mix the chlorine in a plastic bucket IN THE OPEN AIR, before adding it to the tank, and then mixing it as thoroughly as possible with the tank water.

The water will be safe to drink provided the chlorine smell is not to strong.  The recommended range for a free chlorine residual in drinking water is 0.2 to 0.5 ppm.