Home Up Products Saving Energy Glossary Contents About / Contact

Shock Chlorination

There is a chance of bacterial contamination any time there is a new well or a water system fixture such as a pump is removed from a well and replaced.  Bacterial problems are most common in shallow wells and areas with coarse textured soils and fractured bedrock or limestone. The major source of contamination is surface water, or septic tanks or sewage lines located too close to the well. Runoff or leaching from livestock operations can also contaminate wells. 

Shock chlorination procedure:

  • Select a time when well water will not be used for at least 24 hours. Store enough drinking water for this period or do the procedure before leaving for a short trip
  • Determine how much laundry bleach or dry calcium hypochlorite tables are needed. This depends on the diameter of the well and the height of standing water in the well. The height of standing water is the difference between the well depth and the distance from the top of the well down to the water level.  Recommended amounts of laundry bleach are shown within the table below.  If iron bacteria are a problem, concentrations of 800 milligrams per liter may be necessary.
  • Mix the proper amount of chlorine with water in a 5-gallon or larger container and pour the solution directly into the well.
  • Turn on the outdoor faucet nearest the well and let the water run until a strong odor of chlorine is detected. 
  • Turn the faucet off. Connect a garden hose to the faucet and attach a spray nozzle to the end of the hose. Thoroughly wash down the entire inside surface of the well casing with the spray nozzle for at least 15 minutes.
  • After washing the inside of the well casing, turn on all outdoor and indoor faucets one at a time until a strong chlorine odor is detected at each location. Turn each faucet off when the chlorine odor is detected
  • Let the chlorinated water stand in the well and plumbing for at least 24 hours. Do not drink the chlorinated water during this period. You may flush the toilets, but try to minimize the number of flushes.
  • After 24 hours, completely flush the system of chlorine by turning on all outdoor faucets and running them until the chlorine odor is gone. Do not run the indoor faucets until the odor dissipates to prevent damage to the septic system.  Caution: Do not allow more than 100 gallons to flow from system faucets and drains into the septic tank
  • Finally, turn on the indoor faucets until the chlorine odor is gone. You may notice a slight chlorine taste or odor in the water for a few days.

Test the water for bacteria two weeks after shock chlorination to see if you have a recurring problem. Contact your local Health Department for information on water testing and well protection.

Shock chlorination can be done using ordinary laundry bleach (containing approx. 5.25 percent sodium hypochlorite right out of the jug) or calcium hypochlorite (containing 65%-75% available chlorine). The goal is to add enough chlorine to raise the chlorine concentration in the well to about 200 milligrams per liter to kill potentially harmful bacteria and viruses. 

A thorough shock chlorination of the well and water system may destroy all iron bacteria colonies. However, if iron bacteria have penetrated the water-bearing formation they will be difficult to eliminate and will likely re-infest the system. In this situation you will need to repeat chlorination treatment periodically.

 

DUG WELL (3 Diameter)

DRILLED WELL (6 Diameter)

Water Depth

Bleach 5%

Water Depth

Bleach 5%

Feet

Metres

Quarts

Litres

Feet

Metres

Ounces

ml

5

1.5

1

1.1

25

7.6

5

140

10

3.0

2

2.2

50

15.0

10

280

15

4.5

3

3.3

75

22.8

15

420

20

6.0

4

4.4

100

30.0

20

560

25

7.5

5

5.5

125

38.0

25

700

30

9.0

6

6.6

150

45.0

30

840

35

10.5

7

7.5

175

53.0

35

980

40

12.0

8

8.8

200

61.0

40

1220

 

Home Up Products Saving Energy Glossary Contents About / Contact

 

Contact Us: Telephone:  toll free at 1-888-810-4709 Parry Sound,Northern Ontario,Muskoka and Georgian Bay
Send mail  Linda  with questions or comments about our product or web site.

Ontario,Canada Copyright 2017, STRATEnerGY Inc.    All Rights Reserved Caribbean and US
Last modified: November 13, 2018