WLS-011 Disinfecting Wells

Permit and Resource Management Department Banner 750

Revised 10/18/2005
  1. If the water is cloudy, pump the well until the water appears to be relatively clear.
  2. Stop the pump. Add household chlorine bleach directly into the well casing based on the attached table. Do not use scented bleach or swimming pool products containing stabilized chlorine.
  3. Allow the well to stand for 30 minutes to allow chlorine to mix in the well water. After 30 minutes, surge the well alternately by starting and stopping the pump in order to wash down the inside of the casing and the drop line with chlorinated water.
  4. Open the taps, faucets and hydrants at the farthest ends of the water system and at "dead ends" until chlorine odor is detected. Close the taps, faucets and hydrants.
  5. Stop the pump. Do not operate the pump for 24 hours to let the chlorinated water stand in the well, storage tank and any piping in the house.
  6. After 24 hours open all outside taps, faucets or hydrants and let the water flow until the odor of chlorine is gone. Do not discharge heavily chlorinated water into an individual sewage disposal system.
  7. A water sample for bacteriological analysis should be obtained one week or more after disinfecting the well.

The following laboratories are state certified for this purpose:

Bacteriological testing

Sonoma County Public Health Lab
3313 Chanate Road
Santa Rosa, CA 95404
(707) 576-4711

Far West Laboratories Inc
P.O. Box 355
Riverbank, CA 95367
(209) 869-9260

Scott Laboratories
220 Pine View Way
Petaluma, CA 95954
(707) 765-6666

Chemical & Bacteriological testing

Brelje and Race Laboratories Inc
425 South E Street
Santa Rosa, CA 95404
(707) 544-8807

CalTest Analytical Laboratory
1885 N. Kelly Road
Napa, CA 94558
(707) 258-4000

Note:Make sure that the well is tightly sealed to keep out rodents, insects, dirt and surface water seepage.

Amount of Chlorine to Add

Chlorine Compound Required to Dose 100 feet of pipe at 50 parts per million (ppm)

Diameter of pipe or casing5% Available Chlorine (Purex, Clorox)
2 inches 2 ounces
4 inches9 ounces
6 inches20 ounces
8 inches2 1/8 pints
10 inches3 1/2 pints
12 inches5 pints
16 inches1 gallon
20 inches1 2/3 gallons
24 inches2 1/3 gallons

Where wells to be treated are of unknown depth or volume, at least 1 pound of 70% available chlorine or one gallon of household bleach such as Clorox or Purex (5.25% chlorine) may be added in lieu of the use of above table.