1) Use common household bleach as the chlorine source for
[Bleach products usually contain 5 to 6 percent chlorine. For the
disinfection procedure to be effective, the pH (acidity) of the well
water should be between 6 to 7.5. If it is not in this range, then a
well treatment professional experienced in disinfection of high pH
water should be consulted to adjust the pH and maintain it in the
correct range during the disinfection process.
2) Find the total depth of water in the well.
[For example - If the well is drilled to 200 feet and the water level
is 50 feet down from the top, then there is a 150 feet depth of water
in the well]
3) Determine how many gallons of water are stored in the
vertical column of the well. Once you know depth you can work out the
gallons. (See Table 1 for specific Water Volumes)
Well diameter gallons per foot of well gallons in 100 feet
4-inch 0.65 65
6-inch 1.47 147
8-inch 2.61 261
[NOTE - disinfection is not feasible for large-diameter dug wells]
4) Work out how much bleach will be needed: For every 50
gallons of water in the well use one quart of laundry bleach - (4
quarts in a gallon). Do not use excessive amounts of bleach - more is
not more effective.
[In most cases, one gallon of bleach will disinfect 200 gallons of
well water at a chlorine concentration between 200 to 300 ppm (parts
[NOTE - Bleach loses strength in its container over time, Check the
“sell by date” and use bleach that is less than three months old. Use
unscented bleach to avoid adding unneeded chemicals to the water (It
is usually less expensive too)]
5) For best results the bleach should be combined with
water before adding it to the well.
[By reducing the concentration there is less chance of corrosion of
the cables and pipes in the well. The greater volume of water helps
get the chlorine mixed in the well column.]
[NOTE: - Do not mix chlorine solutions with other cleaning products,
including ammonia, because toxic gases will be created.
6) Make the Chlorine-Water Mixture by filling a five
gallon bucket with water and adding about one quart of bleach. Pour
the mixture into the well and repeat until the right amount of bleach
has been added to the well (see #4 above).
7) Remove the well cap and pour the mixture directly down
inside the well casing.
[NOTE - Wear rubber gloves and safety glasses to protect skin and eyes
from splashes. Spills contacting the body should be rinsed
immediately and thoroughly with fresh water.]
8) Recirculate the water in the well by running water with
a hose back into the well for 30 minutes.
[This will help draw the Chlorine-Water Mixture down the well and will
wash the “dry” portion of the well casing or drilled hole above the
water table more thoroughly.]
9) To disinfect the household plumbing first turn off the
electric or gas supply to the hot water heater. Turn on all the
faucets, shower heads, clothes washers, dish washers and outside
faucets, etc. until there is a chlorine smell at each location.
[NOTE - If you have water conditioning equipment check the owners
manual to see if it is sensitive to chlorination. All equipment in the
water system should be disinfected because it may serve as a safe
haven from which the bacteria may reinfect the system.]
10) Leave the Chlorine-Water Mixture in the plumbing system
and well for 12 to 24 hours before removing the chlorinated water.
[NOTE - During the disinfection process, the well water should not be
used for consumption, so make plans for essential water needs before
you begin the disinfection process!]
11) Remove the chlorinated water from the well by running the
pump and leading a hose from outside faucets to a safe area.
[Don’t put the chlorine solution into a septic system or in a creek or
pond where it may kill fish. Flowers and vegetables may be affected by
12) When the chlorine odor has gone the well flushing is
[If you have difficulty smelling the chlorine odor a swimming pool
chlorine test kit can indicate whether or not there is chlorine
remaining in the well water.]
13) Once the chlorine has been removed from the well water,
the indoor plumbing may be flushed out to the septic or sewer system
to remove the chlorinated water.
[Re-energize the hot water heater. The water supply should now be
14) Wait about 5 to 10 days before resampling the water supply
and testing for bacteria.
[If bacteria are still present, repeat the process. It may take
several treatments to remove long-established bacteria colonies. If
the problem persists, contact a professional familiar with
microbiological contamination in wells.]
15) Repeat testing in three months to confirm treatment
success, and then test annually.