- If you have a water softener, it should
be bypassed.
- Remove the well cap, vent pipe or plug
(vent pipes or plugs are on older wells which may have a sanitary well
seal).
- The gallons of water to be disinfected
must be determined by calculating the total capacity of the private water
system, including water stored in a well casing, cistern or spring
box, pressure tanks, existing plumbing and attached fixtures, and all
related storage, excluding water stored in a pond. See
Table 1.
- A disinfectant solution should be prepared
as calculated from Table 2 or Table
3 and poured into the well. For a new installation, an amount of disinfectant
to make a two hundred and fifty parts per million chlorine solutions shall
be prepared. For an alteration, an amount of disinfectant to make a five
hundred parts per million chlorine solutions shall be prepared.
- Connect a hose to a house spigot and run
water directly into the well until chlorine odor is present in the water.
Thoroughly wash down the sides of the well. Continue to run the water
for another 10 minutes.
- Shut off the water to the hose and open
each water fixture in the house (bathroom sinks, bathtubs, kitchen sinks,
showers, and utility room sinks - no need to worry about toilets or laundry).
Let water run through each fixture until chlorine odor is present. Include
both hot and cold water valves.
- Close all valves or fixtures. Recap the
well or replace the vent pipe or plug. Do not use any water for
at least 8 hours. (Toilets may be flushed as needed.)
- Open the hose spigot and discharge the
water to the ground surface or a drainage ditch until the chlorine odor
disappears (do not run this into the septic system, because the amount
of chlorine will upset the septic tank). Open every water fixture in the
house. Let water run through each fixture until chlorine odor disappears.
Include both hot and cold water valves. (The amount of chlorine in the
pipes is not enough to cause a problem in the septic system.)
- The well should now be properly disinfected.
Contact your local health department to schedule a water sample before
using it (new or altered wells only).
When calcium hypochlorite chlorine is used
for disinfection, the tablets or granules must be dissolved in water before
pouring it into the well. Sodium hypochlorite (liquid) solutions must be
used within the manufacturer’s posted expiration date. Sodium hypochlorite
solutions with fragrance additives must not be used for disinfection
of private water systems. Sodium hypochlorite and calcium hypochlorite must
not be mixed with other chemicals for disinfection purposes and all manufacturers’
directions must be followed. Calcium hypochlorite products should not be
used to disinfect wells completed in limestone aquifers, or where water
in the well has high levels of dissolved calcium.
| Table
1 - Volume of water in well |
| Diameter
of well (inches) |
Gallons
per foot of water |
| 3 |
0.37 |
| 4 |
0.65 |
| 5 |
1.0 |
| 6 |
1.5 |
| 8 |
2.6 |
| Table
2 - Amount of Chlorine added to 100 gallons for disinfection |
| Chlorine
concentration (parts per million) |
Gallons
of 5.25 % Sodium hypochlorite (liquid bleach) |
Pounds
of dry Sodium hypochlorite |
Minimum
contact time |
| 250
ppm |
0.5 |
0.38 |
8
hours |
| 500
ppm |
1.0 |
0.75 |
8
hours |
| Table
3 - Quantity of disinfectant for a bored or dug well |
| Diameter
of well (feet) |
Amount
of 5.25 % Sodium hypochlorite per foot of water |
Amount
of 68 % chlorine granules per foot of water |
| 3 |
0.15
gallons (2.5 cups) |
2
ounces |
| 4 |
0.25
gallons (4 cups) |
3
ounces |
| 5 |
0.4
gallons (6 cups) |
4
ounces |
| 6 |
0.5
gallons (8 cups) |
6
ounces |
| 7 |
0.75
gallons (12 cups) |
8
ounces |
| 8 |
1
gallon (16 cups) |
10
ounces |
| 10 |
1.5
gallons (24 cups) |
1
pound |
For example, a new drilled well with a 4
inch casing that is 100 feet deep, contains 65 gallons of water (from Table
1). Since it is a new well we want to use a chlorine concentration
of 250 ppm. (from number 3 above). Since liquid bleach is readily accessible
at the grocery store, we will use that. From Table 2, we need to use 0.5
gallons of bleach for 100 gallons. It is ok to use more than the 65 gallons
in the well, since we need to account for the amount of water in the house.
Once we have run the solution through the entire system, we will shut every
thing off and let it set for at least 8 hours.
