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Disinfection of Private Wells Revised 1/98

Prior to actually disinfecting your well, some consideration should be given to the reason you need this procedure in the first place.  The cause or causes for contamination should be fully investigated prior to disinfection.  Remember, if the cause is not located it could recur at some future time without definite water symptoms and possibly disastrous effects.  Take some time and consider the possibilities.  If you do not know where to start, consider your well a closed system that nothing should be capable of entering.  If you feel there is even a small crack where liquids may seep in, or insects could crawl into your water system, or perhaps circumstances where high rainfalls may flood the area around your well, the water supply is not safe and needs corrective action before you begin disinfection.  You may be able to use common sense to effect a correction, or call your favorite well contractor for help.  If you need the names of reputable contractors in your area, call our office for a list,  or the local Health Department or area sanitarian.  Again, remember this process is only a temporary solution to largely bacterial contamination problem.  If possible, a cause should be found to eliminate future occurrences.  It may not be effective against the cyst forms of such protozoa as Giardia and Cryptosporidium species (depending on concentration of chlorine and exposure time etc.).  Springs can vary in so many ways, we suggest you call our office, the Health Department or the Pennsylvania  Department of Environmental Protection for more specific instructions regarding disinfection procedures.  However, the basic principles discussed here still apply.

This procedure should not be rushed.  It requires time, serious preparation, proper methods and materials, and calm deliberation.  You should make arrangements for drinking water until the situation is resolved (probably several days)  and be prepared to minimize your total use of water for about 24 hours.  Boil water (bring to a rolling boil for at least one minute) and store for drinking or purchase bottled water. During disinfection avoid all heavy uses of water such as laundry, bathing or watering etc. (high chlorine levels may render your water unusable for these purposes in any case).   Although you can flush the toilets on occasion, this too should be minimized during the process.  Do not drink highly chlorinated water.  PLEASE REMEMBER, your water should be considered CONTAMINATED until a sample, totally free of any residual chlorine, has been analyzed by the laboratory and found to be potable.  Water should always be held suspect if there is a sudden change in taste, odor or color.  Always have the source tested and seriously consider chlorination following new construction or any repairs that open the system (work on pumps, pipes, tanks etc.).  Periodic bacterial examinations of private wells should be a part of any home health and maintenance program (due to the reasons listed above or, in the absence of such symptoms, at least yearly).


Disinfection Process and Materials

Suggested Materials
Two to five gallon bucket
Large mason type jar and lid 
Hose and on/off nozzle
One gallon container (if not sure about bucket volume)  
Try to locate an outside tap
Tools necessary to open the well or vault cap   
Parts necessary to re-seal and secure the well or vault
Container to resample well for lab check
Fresh chlorine solution (Sodium hypochlorite usually 5-6%) or chlorine granules (Calcium hypochlorite usually 60-70%).  Obtain a gallon or more of liquid bleach or eight ounces or so of chlorine granules.  Clorox bleach or another liquid chlorine bleach without soaps or conditioners is cheap and easy to obtain (although, higher concentration hypochlorite solutions will require less to do the job).  Solid material should be dissolved prior to use in the well.  This adds an extra step and can be messy.  Follow the manufacturers' recommendations for handling and mixing any of these products. In either case, use fresh material to insure potency.


Chlorination Process
1. COMPLETELY READ THESE DIRECTIONS AT LEAST ONCE BEFORE STARTING.  Understand what you are doing completely or hire a plumber or well contractor if needed.

2. Remove the cover or cap to the well so you gain access to the water.  Make sure you have replacement gaskets or other parts as necessary to properly re-seal the well before proceeding.

3. If using the liquid chlorine material, fill your bucket with water and add one or two ounces of chlorine solution from the gallon jug.  Mix and set aside for the time being.  If using solid material, mix it with the water in the bucket. Dissolve as much as possible producing a liquid chlorine solution.  You may need to use several buckets of water to dissolve the majority of the solid material.  Once dissolved, proceed as you would with the liquid chlorine material below.  Save a few ounces of the mixture to produce a more dilute chlorine solution in a final bucket of water (as done with the bucket set aside with the liquid material above).

4. Using the liquid material, pour the contents of the gallon jug (or the solution you create) down the interior wall of the well casing.  If using the solid material, pour the liquid material only down the interior wall of the well casing, being careful not to pour any solid chlorine material into the well.

5. Use a small amount of the dilute chlorine solution that has been set aside to rinse the well cap.  Carefully pour the rest down the inside wall of the well casing.  The purpose of these rinses is to remove and/or disinfect any dirt. mud or debris that may be clinging to the walls of the well.  This may be far below your line of sight.  The second dilute rinse is to remove the majority of the higher concentration chlorine from well fittings, wires and parts to avoid corrosion or deterioration.  Judge for yourself if additional diluted rinses are needed.  The depth to water, well depth and materials involved all enter into this consideration.  Alternately, you may recirculate water via the hose connection back into the well to rinse all surfaces.

6. Unless you have a very deep well with a large amount of standing water, replace the caps and seals properly and wait about 30 to 45 minutes.  After this time, select a cold water tap inside the house and run the water until you get a strong odor of chlorine.  This may take 10 or 15 minutes.  If no odor of chlorine is detected you may need to recirculate water in the well to mix the chlorine solution (or you may not have added enough chlorine solution for your particular conditions).  To circulate water, attach a hose to a cold water tap and place the hose down the well.  Turn on the water and recirculate until the water coming out of the hose has a strong odor of chlorine.  Make sure the well is then sealed.

7. Next, proceed to all the cold water outlets on the plumbing system and run them until you notice the strong odor of chlorine.  Flush the toilets (once the tap in the bathroom has been done), and run cold water in the tubs and showers.  Select one hot water tap and allow it to run for about a minute to get treated water from the well to the hot water heater.  Normally, hot water lines do not need to be treated as heating limits bacterial growth, however, in the case of new construction or repairs involving the hot water system it  may be advisable to treat both hot and cold water systems.

8. Minimize the use of water for 12 to 24 hours.  We recommend the longer period.

9. Select a cold water tap OUTSIDE and connect a hose.  Depending on the well's ability to produce water, run water constantly from the well to clear the chlorine solution.  It may take several hours to several days depending on your ability to remove water from the well.  If the well will support it,  try setting the flow to about two gallons per minute using a gallon jug (hose flow should fill the jug every 30 seconds) and allow it to run over night.  Since you may become desensitized to the odor of chlorine, you can not depend on your sense of smell to determine when all the chlorine is gone.  In the absence of a test kit, use a large mason jar (1 quart), fill it half way with the water in question, cap and shake the contents vigorously, then quickly remove the lid and smell the air layer inside the jar.  There should be NO odor of chlorine at all.

10. Once you are sure the chlorine is gone you should collect a sample for analysis.  It is very important that ALL the chlorine be gone.  A small residual can yield false negative results.  This convenient condition could change once ALL chlorine traces vanish.  You may wish to wait several days after a you no longer detect chlorine for a test or test it more than once over an extended period of time.  REMEMBER:  CONSIDER YOUR WATER CONTAMINATED UNTIL LAB RESULTS CONFIRM NO PROBLEMS.