Disinfecting Wells
If you suspect that your well may be contaminated, contact your local
or state health department or agriculture extension agent for specific
advice. Here are some general instructions for disinfecting wells.
To Disinfect Bored or Dug
Wells
-
Use Table 1
(below) to calculate how much bleach (liquid or
granules) to use.
-
To determine the exact amount to use, multiply the
amount of disinfectant needed (according to the diameter of the
well) by the depth of the well. For example, a well 5 feet in
diameter requires 4 1/2 cups of bleach per foot of water. If the
well is 30 feet deep multiply 4 1/2 by 30 to determine the total
cups of bleach required (4 1/2 X 30 = 135 cups). There are sixteen
cups in each gallon of liquid bleach .
-
Add this total amount of disinfectant to about 10
gallons of water. Splash the mixture around the wall or lining of
the well. Be certain the disinfectant solution contacts all parts
of the well.
-
Seal the well top.
-
Open all faucets and pump water until a strong odor
of bleach is noticeable at each faucet. Then stop the pump and
allow the solution to remain in the well overnight.
-
The next day, operate the pump by turning on all
faucets, continuing until the chlorine odor disappears. Adjust the
flow of water faucets or fixtures that discharge to septic systems
to a low flow to avoid overloading the disposal system.
| Table 1. Bleach
for a Bored or Dug Well |
| Diameter of well (in feet) |
Amount of 5.25% laundry breach chlorine per foot of
water |
Amount of 70% chlorine granules per foot of water
|
| 3 |
1 1/2 cups |
1 ounce |
| 4 |
3 cups |
2 ounces |
| 5 |
41/2 cups |
3 ounces |
| 6 |
6 cups |
4 ounces |
| 7 |
9 cups |
6 ounces |
| 8 |
12 cups |
8 ounces |
| 10 |
18 cups |
12 ounces |
| Source: Illinois Department of Public Health.
Recommendations may vary from state to state.
|
To Disinfect Drilled
Wells
-
Determine the amount of water in the well by
multiplying the gallons per foot by the depth of the well in feet.
For example, a well with a 6-inch diameter contains 1.5 gallons of
water per foot. If the well is 120 feet deep, multiply 1.5 by 120
(1.5 X 120 = 180).
-
For each 100 gallons of water in the well, use the
amount of chlorine (liquid or granules) indicated in Table 2. Mix
the total amount of liquid or granules with about 10 gallons of
water.
-
Pour the solution into the top of the well before
the seal is installed.
-
Connect a hose from a faucet on the discharge side
of the pressure tank to the well casing top. Start the pump. Spray
the water back into the well and wash the sides of the casing for
at least 15 minutes.
-
Open every faucet in the system and let the water
run until the smell of chlorine can be detected. Then close all
the faucets and seal the top of the well.
-
Let stand for several hours, preferably overnight.
-
After you have let the water stand, operate the pump
by turning on all faucets continuing until all odor of chlorine
disappears. Adjust the flow of water from faucets or fixtures that
discharge into septic tank systems to a low flow to avoid
overloading the disposal system.
| Table 2. Bleach
for a Drilled Well |
Diameter of Well
(in inches) |
Gallons
per foot of water |
| 3 |
0.37 |
| 4 |
0.65 |
| 5 |
1.0 |
| 6 |
1.5 |
| 8 |
2.6 |
| 10 |
4.1 |
| 12 |
6.0 |
Amount
of Disinfectant Required
for each 100 gallons of water
|
| Laundry Bleach (5.25% Chlorine) |
3 cups* |
| Hypochloride Granules (70% Chlorine) |
2 ounces** |
*1 cup = 8-ounce measuring cup
**1 ounce = 2
heaping tablespoons of granules
Source: Illinois Department of Public
Health.
Recommendations may vary from state to state.
|
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