Wells in the Vanguard, Sask., area had to be shock chlorinated after July’s flood to reduce bacterial levels.
But Randy Beler, rural water quality technician with Sask Water, says shock chlorination should be part of regular well maintenance, and not just an emergency measure.
“We recommend shock chlorinating wells every six months to help control bacterial growth,” he said.
Shock chlorination requires a clean water tank with a holding capacity of at least 1,400 litres, a garden hose and 20 litres of industrial strength chlorine (12 percent sodium hypochlorite). Chlorine is available from chemical dealers, water treatment suppliers and dairy supply retailers.
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Wells are taken out of service while being shock chlorinated, which means storing enough water for a minimum of 12 hours.
Fill the water tank with well water and add half of the chlorine solution to the tank. The other half of the chlorine is added to the well through the garden hose, extended as near the bottom of the well as possible, to allow thorough mixing.
Slowly add the water from the tank to the well without exceeding the well pumping rate. All outlets, such as taps, toilets, hydrants and livestock waterers, should be run until the chlorine can be smelled. The system should then be turned off for at least 12 hours to allow the chlorine to completely disinfect water lines. This method is more effective than just pouring chlorine down the well because it mixes more fully with the well water rather than floating on the surface.
After 12 hours, the entire system should be flushed until the chlorine smell disappears and the water runs clear. A follow-up bacterial water sample should be delayed for a week to ensure that only untreated aquifer water is being sampled. Shock chlorination disinfects the well, the water in it and the distribution system.
“We caution farmers that once the shock chlorination is complete, it is a necessity to test the water before using it for drinking and other household purposes,” said Dan Runcie, Prairie Farm Rehabilitation Administration district manager.
“If the aquifer has been contaminated, shock chlorination treatment won’t have been effective and users should treat the water adequately or use an alternative source.”
If the aquifer has been contaminated, water is considered safe to drink only after it has shown no contamination after a number of tests over a long period of time, possibly weeks or months.
“Newly constructed wells should also be shocked in order to ensure the integrity of the well water,” Beler said.
Chlorine concentrations at this level are dangerous, so wear protective clothing and eye protection, and avoid inhaling the fumes. Confined spaces such as well pits and crawl spaces should be well ventilated.
For more information about shock chlorination, call Sask Water at 306-778-8257 or PFRA at 306-778-5000.
