567—49.26 (455B) Well disinfection. All new, repaired or rehabilitated wells shall be pumped to waste until the water is free of drilling mud, drill cuttings and sand, and the water is clear. Wells and water systems shall be disinfected by the contractor following completion of construction and whenever any well services have been performed. A chlorine solution such as a sodium or calcium hypochlorite shall be used. Chlorine compounds used for well disinfection must meet NSF Standard 61 and have no additives.
	 49.26(1) The disinfectant shall be dispersed throughout the entire water column in the well. The disinfectant shall also be brought into contact with the inside of the well casing pipe above the static water level.
	 49.26(2) The disinfectant shall remain in the well for a minimum of 2 hours if a concentration of at least 100 mg/L chlorine is achieved, or a minimum of 24 hours if at least 50 mg/L is achieved.
	 49.26(3) For emergency situations, a contact time of a minimum of 30 minutes shall be provided at a chlorine concentration of at least 200 mg/L.
	 49.26(4) The amount of HTH or household bleach required for a chlorine concentration of 200 mg/L is given in the following table:
Table 49.26(4)
Amount of chlorine disinfectant required for every 25 feet of water in well

Well casing diameter (in inches)	4	6	8	12	18	24	30	36	
Amount of pelleted HTH (in ounces containing approx.	70 percent Ca(OCl)2)	0.7	1.5	2.6	5.6	13	23	36	52	
Amount of chlorine bleach (in pints containing 5.25 percent NaOCl)	0.5	1.2	2.1	4.7	10.6	18.8	29.3	42.2	
	 49.26(5) Dry disinfectant shall be dissolved in a separate container of water before introduction into the well. The solution shall contain not more than eight ounces of pelleted HTH disinfectant per five gallons of water.