To disinfect wells, follow these procedures. Charts indicating the proper amount of chlorine to use vary with the type of chlorine purchased. (See tables below.)

  1. Unscrew the vent plug from the well seal.

  2. If using bleach, pour 24 ounces per 100 gallons of water into the well through the vent hole (see table below).

  3. If using granular chlorine/calcium hypochlorite, pour 3 ounces per 100 gallons of water into the well through the vent hole.

    • 6-inch diameter wells have 1.5 gallons of water per 1 foot of well.

    • 24-inch diameter bored wells have 24 gallons of water per 1 foot of well.

  4. If there is a tap at the well head or nearby, connect a hose to it, turn the tap on, and hose down the inside of the well at least 1 hour by placing the hose inside the vent hole. If there is no tap nearby, omit this step.

  5. One at a time, turn on each cold-water tap in the house until you smell chlorine. Include showerheads as well as bathtub taps and flush each toilet once. Run chlorinated water through all other lines including washer, icemaker and dishwasher.

  6. Run one hot-water tap for at least 5 minutes to draw water into the water heater. Close all faucets.

  7. Allow the chlorine to remain in the plumbing system for 24 hours. At the end of the chlorination period, attach a hose to an outside tap and allow the water to run from the hose until you cannot smell the chlorine any longer. Even after the chlorine smell is gone, continue to flush. (If using step 3, continue to recirculate while flushing chlorinated water out of the house.)

NOTE: The chlorinated water may interfere with the bacterial action in your septic tank system. It is recommended that as little chlorinated water as possible be allowed to enter the septic system. When you run the water off at the end of the chlorination period, run the hose as far as possible from your septic system.

NOTE: If your well is capped off underground, it will be necessary to dig it up in order to chlorinate. We STRONGLY recommend that the casing of such wells be extended above ground permanently by either the homeowner or a Certified Well Contractor.

NOTE: To ensure that the chlorination has been effective in your well, you should resample your water at least 24 hours after all chlorine has left the system.

Chlorine is a strong reactive chemical. Use all chemicals in accordance with the label, and NSF approval is recommended.

How much chlorine do I need? 

CHLORINATION WITH 70% CALCIUM HYPOCHLORITE
Well diameter
gallons/foot
50 feet water
100 feet water
200 feet water
300 feet water
400 feet water
2 in.
.16
.16 oz
.32 oz
.64 oz
.96 oz
1.28 oz
4 in.
.65
.63 oz
1.25 oz
2.5 oz
3.75 oz
5.0 oz
6.25 in.
1.59
1.52 oz
3.03 oz
6.06 oz
9.09 oz
12.12 oz
8 in.
2.61
2.5 oz
5.0 oz
10.0 oz
15.0 oz
20.0 oz
20 in.
16.32
16.32 oz
31.26 oz
 
 
 
24 in.
23.50
22.40 oz
44.80 oz
 
 
 
 
CHLORINATION WITH 5.25% SODIUM HYPOCHLORITE
Well diameter
gallons/foot
50 feet water
100 feet water
200 feet water
300 feet water
400 feet water
2 in.
.16
.02 gal
.03 gal
.06 gal
.09 gal
.12 gal
4 in.
.65
.06 gal
.12 gal
.25 gal
.37 gal
.50 gal
6.25 in.
1.59
.15 gal
.30 gal
.61 gal
.91 gal
1.22 gal
8 in.
2.61
.25 gal
.50 gal
.99 gal
1.49 gal
1.99 gal
20 in.
16.32
1.67 gal
3.33 gal
 
 
 
24 in.
23.50
2.67 gal
5.33 gal
 
 
 
 

Since boiling water concentrates levels of nitrates in water, young infants and pregnant women should use bottled water instead of boiled tap water for drinking and cooking after coliform/bacteria confirmation.​