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Review these helpful publications:
These recommendations are from the Private Water System Handbook, Midwest Plan Service, Iowa State University, MWPS-14, 1992
All of these formulas are for common household bleach, like Clorox, Purex, or a generic brand. The label should indicate that the bleach contains 5-6% Sodium Hypochlorite. Do not use bleach with additives or special scents - just plain laundry bleach.
|1/4 cup of 5.25% chlorine laundry bleach per 10 gallons of water|
|3 pints of 5% chlorine bleach per 100 gallons of water = 200 mg/l (ppm) chlorine concentration|
If your system is plumbed such that you must shock chlorinate the water in the holding tank to disinfect your drinking water system, then clean out the tank as much as possible before shocking the system.
|8 cups (1/2 gallon) of chlorine bleach per 1000 gallons of water|
Mix proper amount of chlorine and water together thoroughly and let stand for 20 minutes. If the water does not have a slight chlorine smell, repeat the dosage and wait another 15 minutes. If after the second dosing, the water still does not have a chlorine odor, it isn't suitable as a drinking water source. If the chlorine taste is too strong, let it stand exposed to the air or pour it from one container to another several times.
You may be able to use the water source if you filter it first. Pour a gallon of water through a paper filter or clean cloth. To treat one gallon of water, use 10 drops of chlorine bleach, mix, wait 30 minutes, smell for chlorine. If no odor, repeat the treatment. If after the second dose of bleach, there is still no odor, don't consume the water.
See EPA's fact sheet for information on wells and septic systems
If you need to disinfect drinking water temporarily, such as after a flood or any time bacteria is found in your water, read about using chlorine bleach or boiling to make your water safe:
Emergency Disinfection of Drinking Water (US Environmental Protection Agency)