15A ncac 02c .0111 DISINFECTION OF WATER SUPPLY WELLS
(a) Any person constructing, repairing, testing, or performing maintenance, or installing a pump in a water supply well shall disinfect the well upon completion of construction, repairs, testing, maintenance, or pump installation.
(b) Any person disinfecting a well shall perform disinfection in accordance with the following procedures:
(A) Hypochlorite shall be placed in the well in sufficient quantities to produce a chlorine residual of at least 100 parts per million (ppm) in the well. Stabilized chlorine tablets or hypochlorite products containing fungicides, algaecides, or other disinfectants shall not be used. Chlorine test strips or other quantitative test methods shall be used to confirm the concentration of the chlorine residual.
[Note: About three ounces of hypochlorite containing 65 percent to 75 percent available chlorine is needed per 100 gallons of water for at least a 100 ppm chlorine residual. As an example, a well having a diameter of six inches, has a volume of about 1.5 gallons per foot. If the well has 200 feet of water, the minimum amount of hypochlorite required would be 9 ounces. (1.5 gallons/foot x 200 feet = 300 gallons at 3 ounces per 100 gallons; 3 ounces x 3 = 9 ounces.)]
(B) The hypochlorite shall be placed in the well by one of the following or equivalent methods:
(i) Granular hypochlorite may be dropped in the top of the well and allowed to settle to the bottom; or
(ii) Hypochlorite solutions shall be placed in the bottom of the well by using a bailer or by pouring the solution through the drill rod, hose, or pipe placed in the bottom of the well. The solution shall be flushed out of the drill rod, hose, or pipe by using water or air.
(C) The water in the well shall be agitated or circulated to ensure thorough dispersion of the chlorine.
(D) The well casing, pump column and any other equipment above the water level in the well shall be rinsed with the chlorine solution as a part of the disinfecting process.
(E) The chlorine solution shall stand in the well for a period of at least 24 hours.
(F) The well shall be pumped until there is no detectable total chlorine residual in water pumped from the well before the well is placed in use.
(2) Other materials and methods of disinfection, at least as effective as those in Subparagraph (1) of this Paragraph, may be used upon prior approval by the Department.
History Note: Authority G.S. 87‑87; 87‑88;
Eff. February 1, 1976;
Amended Eff. September 1, 2009, April 1, 2001; December 1, 1992; July 1, 1988; September 1, 1984.