To produce 1% solution from a 10% concentrate, it takes 9 parts water (of drinking water quality) to one part concentrate. For domestic use, we do not recommend making a 6-month supply as it may lose strength over time. In addition, we recommend purchasing new concentrated sodium hypochlorite every several months and stored in a cool dark place to minimize its breakdown. Finally, a local agricultural extension agent may also be able to assist you.
For information on disinfecting private household wells, please visit our Web site at: http://water.epa.gov/drink/info/well/index.cfm.
For information on emergency disinfection of drinking water, please visit our Web site at: http://www.epa.gov/your-drinking-water/emergency-disinfection-drinking-water.