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A Homeowner’s Guide to Well Chlorination

Sources of Contamination:

The two most common causes of bacterial contamination are (a) small animals that get past loose-fitting well caps, or (b) surface water that infiltrates buried wells with poor sanitary seals.

Sealed and vented, state-approved well caps are readily available. Buried wells should be brought above ground level and outfitted with a sealed cap.

Overviews of Chlorination and De-Chlorination:

Chlorination introduces chlorine into the well to be circulated throughout the entire water system. In our opinion, a combination of granular and pelletized chlorine is superior to liquid chlorine (household bleach) because they sink and penetrate the full depth of the well. Liquid chlorine can become trapped for some time in the upper portion of the well.

In wells with high counts of iron and manganese, the chlorine will oxidize the minerals and cause potentially severe staining and clogging of treatment equipment, water fixtures, and plumbing. These potential problems can be minimized as explained below. Chlorine can also cause built up “films” to be sloughed off the inside of pipes.

De-chlorination involves running the water from the bottom of the water storage tank or an outside spigot until it’s clear (no “color”). “Color” is best seen in a volume of water. Use a white five-gallon bucket or a one-gallon, semi-translucent milk jug.

Chlorine Notes:

  • The example below provides a 50 parts per million (ppm) chlorine dosage, which should be more than enough.
    Note: a pool has 1-3 ppm.
  • A gallon of Clorox bleach has 52, 500 ppm of available chlorine.
  • An ounce of household bleach has about 410 ppm of available chlorine.
  • A 1-gram pellet of chlorine has 180 ppm of available chlorine.

You will need to calculate the following:

  • The well capacity in gallons (use the table below)
  • If the well depth is unknown, use 400 gallons as your well’s capacity.
  • The ppms of chlorine needed (gallon capacity x 50).
  • The amount of chlorine needed.

Example: 300 foot, 6” well:

  • 300 feet x 1.47 gallons per foot = 441 gallons
  • 441 gallons x 50 ppm = 22,050 ppm
  • 22,050 ppm ٪ 52,500 = 0.42 gallons of liquid household bleach
  • 22,050 ppm ٪ 180 = 122.5 pellets (1-gram each)
Well Diameter Gallons per foot
4” 0.672
6” 1.47
8” 2.61
24” 23.4
30” 36.6
36” 52.6

The Chlorination Procedure:

  1. Run a garden hose from the water storage tank (preferred) or from an outside faucet back to the well and turn it on to circulate the water.
  2. Pour/drop the chlorine down the well.
  3. Circulate for 20 minutes or until a chlorine odor is strongly detected, then shut off the hose and re-cover the well.  Important note: if the water has a high iron/manganese content water, turning off the hose and chlorinating the house as soon as chlorine is detected can help minimize potential issues caused by the oxidized minerals.
  4. Run water, hot and cold, one fixture at a time, until chlorine is detected. Don’t forget the toilets, the washing machine, the dishwasher, and outside spigots.
  5. Let things sit for at least 6-8 hours or overnight. It’s OK to flush toilets and wash your hands. But you should minimize chlorinated water use.

The De-Chlorination Procedure:

  1. Run a garden hose from the water storage tank (preferred) onto the ground (not back into the well) where the strongly chlorinated water will do the least amount of damage or harm to plants and animals until the water is clear and chlorine-odor free.
  2. Important note: This can take several hours. It’s critical that you monitor the water flow to make certain you don’t run out of water. If you do, shut off the well pump at the circuit breaker and allow the well to recover before continuing the process.
  3. Run the water in the house, hot and cold, until the chlorine is gone.

General Tips:

  • Run the hose to circulate and de-chlorinate directly from the water storage tank if possible.
  • Know where your circuit breaker or pump electrical switch is located before starting the de-chlorination process, just in case you run out of water.
  • If you have an above ground “jet” pump, running out of water may require re-priming.
  • Do not de-chlorinate by running inside faucets or spigots (chlorine is not good for the septic system).
  • Plan for the de-chlorination process to take several hours.
  • Expect some staining.
  • Expect some clogging due to released debris.

As always, please call us at 860-345-4400 if you have any questions.