Heather Kolich, ANR Agent, UGA Extension Forsyth County

Heavy rainfall and flooding can contaminate wells with pollutants and bacteria. Here are actions to take if your private well is overtopped with flood water during a storm.

As soon as possible after flooding, pump a minimum of 2 to 3 times the well volume out of the well. This action helps to clear the well of flood water and potential contaminants, including bacteria. Discard this water from an outside spigot so that 1) potentially contaminated water doesn’t enter indoor plumbing and 2) the excess volume of water doesn’t overwhelm your septic tank. To calculate how much water to pump out, use the formula pictured here:

Mathematical formula to calculate how to shock chlorinate a well.

After the initial pump out, use shock chlorination to disinfect the well by pouring 3 pints of plain, unscented household chlorine bleach per 100 gallons of water into your well. The bleach must stay in the system for 12-24 hours. At the end of the treatment period, pump out another 3 or 4 times the volume of the well. Again, the majority of this water should be discarded from an outside faucet with only a small portion being discarded through indoor faucets. If discharged into the septic tank, this highly chlorinated water could cause problems with bacterial colonies necessary for waste breakdown.

Finally, 1-2 weeks after shock chlorination treatment, have the water tested by a qualified lab to ensure that microbial contaminants are gone and the water is safe for drinking. Water used for drinking or cooking should be boiled until lab testing confirms that it is safe for consumption.