WELL DISINFECTION PROCEDURE

WELL DISINFECTION PROCEDURE

Ford County, Kansas

Planning, Zoning, and Environmental Health

100 Gunsmoke

Dodge City, KS 67801

(620) 227-4739

 

Disinfection is necessary when sampling has indicated the presence of bacteria in a domestic well.  If appropriate, the well construction should be brought up to current State standards so that it is properly drained, sealed, and vented.  Because reconstruction can introduce bacteria, disinfection must be completed before the well is put back into service.  The procedure is as follows:

 

1.      Use a CLEAN container with more than 30 gallons capacity.  A new garbage can works well.  Add the appropriate amount of bleach (see chart below) to the container and fill with water.

 

2.      To determine the depth of casing, use a string or cord at least 200 feet long and fasten a weight to one end.  Lower the weight to the bottom of the well and mark the cord to indicate the top of the casing.  Pull up the cord, watching for the point where it became wet, and mark that point.  Pull up the remaining string and measure the length, which was wet.

 

Text Box: Casing Diameter		Oz. Bleach		Depth of Casing		Amount of Bleach
	4 inches		     .5 oz	x	     ____ ft	     =  	    	 _____oz

	5 inches		     .8 oz	x	     ____ ft	     =  	     	_____oz

	6 inches		   1.2 oz	x	     ____ ft	    =  	    	 _____ oz

8 inches		   2.1 oz	x	     ____ ft	    =  	    	 _____ oz
	
EXAMPLE:
Casing Diameter		Oz. Bleach		Depth of casing		Total Bleach
	5”			   .8 oz	x	   100 Foot		= 	     80 oz.

           

 

 

 

 

 

 

 

 

 

 

3.      Remove the sanitary well cap and pour or siphon the bleach solution into the well.  Put the well cap into the empty solution container to keep it clean.

 

4.      Attach a garden hose to the nearest sill cock or hydrant, and run water until bleach or chlorine solution is smelled.  Use some of the solution to clean the end of the hose.  Run some solution into the bucket to cover the well cap.  Direct the end of the hose into the open well casing and run water into the well so that the solution will wash down the interior of the casing and any piping or cables present.  Allow the water to run for five minutes then shut the tap.  Wait five minutes, then turn on the water for two minutes and shut off for two minutes.  Repeat with one minute, and with 30 seconds.

 

5.      Close the tap and reseal the well casing.

 

6.      Go to each additional outside outlet and open the tap until bleach is smelled, then shut the tap.  Repeat this procedure at all inside points of discharge in the distribution, such as faucets, toilets, showers, etc.  Chlorinated water should be distributed throughout the entire water system.

 

7.      Allow the chlorinated water to remain in the system for at least 12 hours (or overnight).  DO NOT DRINK FROM THE SYSTEM OR DO LAUNDRY DURING THIS TIME.

 

8.      Return to the outside tap and flush water until there is no detectable chlorine odor (have someone who has not been working with the disinfection procedure smell for chlorine) and shut the tap.  Avoid flushing to the sewer system.  Repeat this procedure at all other points of discharge as previously described to flush the entire water system.

 

Resume normal water use, EXCEPT FOR DRINKING OR FOOD PREPARATION.  After three (3) or more days, the water should be checked for chlorine residual and if free of chlorine, the water may be re-sampled.

 

 

CHECKING FOR CHLORINE RESIDUAL

 

  1. After chlorinating the well, wait three days and if no chlorine smell is detectable, obtain approximately one teaspoon of water.

 

  1. Tear open the small foil packet marked “Chlorine Total-DPD” and empty the powdered contents into the water in the cup.

 

  1. Swirl to dissolve the powder, place the cup on a sheet of white paper, and IMMEDIATELY look for a pink color in the water.

**If the water is clear, proceed with collecting the water sample.

**If the water is even slightly pink, some chlorine is still in the system and more flushing is necessary before collecting the sample.

 

When a well has been submerged, surrounded with floodwaters, or otherwise affected by nearby flooding, it is wise to assume that contamination has occurred.  Removal of mud and debris is necessary before disinfection can be effective.  If the well does not have a State approved well cap, if the casing does not extend at least 12” above the natural ground level, or if there are other construction defects, it should be reconstructed so that it is properly drained, sealed, and vented.  A certified well driller can assist or you may contact the Ford County Planning, Zoning, and Environmental Health Department at (620) 227-4739.

 

PREPARING THE WELL FOR DISINFECTION

 

  1. Remove all mud, silt, and sediment from the well before removal of the well cap.
  2. Pump the well out thoroughly to remove all floodwater.  The existing well pump may be used if operable.  Pump to a ditch until the discharge is clear.  Catch water in a clear glass and look for cloudiness.  If cloudy, continue pumping until the water is clear.
  3. Make appropriate corrections to the well construction.  See underlined portion above.)  Pump the well to assure that the water remains clear.  Proceed with disinfection.