How To Shock A Well

It is important to sanitize a well twice a year, whether it is a new well or an existing well. If the well has been disrupted for service or repair, it is a must that it be sanitized. The well storage tank, pipelines, and fixtures should be rinsed with a strong sanitizing solution to kill all harmful pollutants.

Krudico Chlorine Pellets and Granules can be used for well, storage tank, or cistern sanitation. The amount of tablets and granules used will depend on the amount of water in the system to be sanitized. A 50 ppm chlorine concentration is ideal for sanitizing a well. To produce a 50 ppm chlorine concentration, used 1 oz. of pellets or granules for each 100 gallons of water in the system. (1 oz. granules/ 100 gal. = 35 pellets/ 100 gal.). If the water has a high iron or sulfur content, more chlorine may be needed to achieve a 50 ppm chlorine residual.

  1. Bypass the water softener, other filters, or purification equipment.
  2. Remove the cap or seal from the casing and, if possible, then measure the depth of the water in the well, then refer to the Table (#10) below to determine how much chlorine should be used. In some instances removing the seal to measure the water can be a difficult task. It may be easier to estimate well and water depth from well log or other records. As a general rule, it is better to use too much chlorine than too little. If too much chlorine is used, it will simply take longer for the taste and odor to leave the system. Not enough chlorine may allow some harmful pollutants to survive.
  3. Use a pipe to get by any restrictions in the well, a 10’ length of 3/4" PVC is usually ideal.(If it is not possible to remove the well cap, remove vent or sanitation access plug.)
  4. Drop one tablet into the well and listen to hear if it hits the water (you will hear a “plunk” sound). If the tablet hits the water drop one-half (1/2) of the determined amount of chlorine tablets needed into the well. These will sink to the bottom and sanitize the lower portion of the well.
  5. Mix half of the determined amount of granules in a clean, plastic, five (5) gallon container of water and pour the solution down the well to sanitize the upper portion of the well.
  6. It is necessary to recirculate the water in the well to mix the chlorine thoroughly throughout the entire water system. Connect a hose to an outside silcock that is located after the pressure tank and run water back down the well (this also rinses upper portions of the well). After about 15 minutes of recirculation of the water, a strong chlorine odor should be present, if not, repeat steps 4 and 5. Run water through service line until you detect chlorine odor in all taps.
  7. Allow the sanitized water to stand in the system for at least six (6) hours, and preferably overnight. Open an outside faucet and flush system until water runs chlorine free (until you don’t smell any chlorine). Repeat flush operation on each faucet in the system.
    1. Chlorine may make the water run colored, and iron deposits, slime and organic material may break loose and plug pump screens. DO NOT CONTINUE TO RUN PUMP IF WATER DOES NOT FLOW.
    2. The high level of chlorine required to sanitize a water system is corrosive to most
      metal and the chlorine solution must not remain in the water system more than thirty-six (36) hours before completely flushing from the system.
  8. Return all equipment to service position.
  9. After 2-3 weeks the water should be tested.  If bacteria, iron bacteria, sulfur, or other

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