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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.
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.
**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.