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Unsanitary Well Water and Well Disinfection
It is not that unusual for a typical rural well to test positive for the presence of Coliform bacteria (those bacteria - there are many species - that are associated with the waste of humans and other animals), this condition is unacceptable. Because the condition of well water is subject to change all agencies and laboratories recommend testing well water for the presence of Coliform bacteria on an annual basis. If your well has tested positive for Coliform bacteria, disinfection is easily achieved in most cases. Below you will find procedures for Well Water Disinfection.
Procedures for Well Disinfection
Following are three DEFINATIVE procedures for the disinfection of water wells. The first procedure is offered by a local (NY) laboratory that performs well water sample analysis, Yorktown Medical Laboratory. This procedure is preferred by Reveal Home Inspections because it is the most rigorous. However, in most cases, the other procedures will certainly do the job as well. The second procedure is offered by the Putnam County Department of Health. And the third procedure is offered by the New York State Department of Health. All three procedures are quoted directly from official publications published by each entity.
Reveal Home Inspections will not be responsible for any damage as a result of employing any of the following disinfection procedures.
Yorktown Medical Lab (Environmental Services)
Wells which have been altered, repaired, newly constructed, or accidentally polluted should be thoroughly disinfected before being put into use. A sample of water must be taken for bacteriological examination after the disinfection procedure is complete to be certain that the procedure has been effective, and that the water is of an acceptable sanitary quality to be consumed.
The following suggested procedure is usually sufficient in scope to disinfect most wells. However, occasionally due to unpredictable environmental factors, this procedure may need to be performed several consecutive times to achieve water of an acceptable quality. It must be understood that this procedure is an interim one, and may not correct some water source problems, such as those with reoccurring sources of contamination. Indeed, before disinfecting the area around the well and well itself should be inspected to be sure the source of water is secure against the outside environment and that all obvious possible sources of contamination have been identified and corrected.
1) Mix one gallon of common laundry bleach (such as Clorox, Dazzle, Etc.), which has about 5.25% active chlorine, in three gallons of tap water, in a bucket. Use caution, bleach will stain clothing. Pour this mixture into the well head. Use 1 gallon of bleach for every 100 feet of well depth.
2) Attach a garden hose to an outside tap and lead the other end into the well head. Put about five feet of hose down into the well cavity to assure that it doesnt fall out. Turn on the outside tap and allow well water to flow into the well head for the next five hours. This will cause the well water to be recirculated through the tank and the well cavity, increasing the contact time for the chlorine and improving disinfecting ability of the chlorine throughout the entire well cavity. NOTE: Some wells do not have casings. Wells of this type should omit this step.
After the five hour circulation, turn off the outside tap and remove the hose from the well. Cap the well and make it secure.
3) Go into the building and, one by one, open each tap for one minute to bring chlorinated water from the well to the end of the particular service line. This should be done for tub taps and shower heads as well. Flush each toilet once, one by one. Allow the system to sit like this undisturbed for 12 hours (overnight is good).
4) After the 12 hour period, take the hose and lead it out away from shrubs and the building. Turn on the outside tap and allow the chlorinated well water to flush out of the system to purge the chlorine by placing a demand on the underground source of fresh, untainted water. After no more chlorine odor is detected from the water flowing from the hose, shut it off. Go inside the building and allow each tap to run, one by one, for 10 minutes to clear out the chlorinated water. Flush each toilet twice, one by one.
CAUTION! If your water source has a history of poor water supply volume, constant purging may deplete your water and cause damage to the pump. In such case, purge the chlorine over several days of intermittent water use. YML (and Reveal Home Inspections) will not be responsible for any damage as a result of following this suggested disinfection procedure.
5) The disinfection should now be complete. Test the water for total coliform bacteria three days after this procedure is done, and 14 days later to assure that the sanitary quality is acceptable. The first sample should also be tested at the same time for free chlorine to be sure that none of this disinfectant remains in the water - its presence would make testing for bacteria invalid.
IMPORTANT NOTE: Until the water supply is shown to be of acceptable sanitary quality, the water should not be used for drinking.
Putnam County Department Of Health
Division Of Environmental Health Services (914) 278-6130
Disinfection Of Well
The following procedure should be used after completion of a new drilled well, the repair or renovation of any well or when any well tests unsatisfactory for bacteria.
1) For each 50 foot depth, mix one quart of plain laundry bleach containing 5 ¼% chlorine in 5 gallons of water.
2) Pour the solution into the well. Run a hose from an outside faucet in to the well, then start the pump. (This pulls the disinfecting solution into the storage tank faster.)
3) Allow water to flow from each tap until a chlorine odor is detected. Where possible, remove the plug on top of the pressure tank and allow the solution to fill the tank completely, then turn off the pump.
4) Allow the solution to remain in the system for at least 8 hours or preferably overnight.
5) Drain the pressure tank and replace the plug. Start the pump and allow water to flow to waste from each tap until the chlorine odor disappears.
To avoid disruption to the septic tank processes, discharge of the chlorine solution in the system should be done by taking a garden hose and attaching it to the valve at the bottom of the water storage tank (usually in the basement). The valve should then be turned on and the water should be discharged out onto the ground in the yard. When most of the storage tank water has been flushed, check the odor of the water coming out of the hose. When the chlorine smell has nearly disappeared, open up other faucets in the house for 15 minutes or until the smell of chlorine is not detected.
6) Use the water normally except for drinking and cooking purposes for one week. Collect a sample of water in a laboratory container for bacteria analysis. Any NYS DOH ELAP Laboratory (Environmental Laboratory Approval Program) can be used for the analysis. It is also of equal importance that you retest 7-10 days after disinfection for coliform bacteria. If there is no problem with contamination, the water test after 10 days will remain good if the disinfection was done properly.
7) Should the bacteria re-test fail, this procedure may be followed again or contact the well driller or this department at (845) 278-6130 for further assistance.
New York State Department Of Health
Albany, NY 800-458-1158
After a well is constructed and pumped clear, or after any improvements are made, (or, if a laboratory examination of a water sample reveals bacteriological contamination) it should be disinfected with a chlorine bleach. Bleaches containing 5.25 per cent available chlorine are sold in supermarkets and grocery stores under such names as Clorox, Dazzle, Purex, White Sail, 101 etc. Here is the procedure for disinfecting a well:
1) Mix two quarts of bleach in ten gallons of water. Pour the solution into the well while it is being pumped. Keep pumping until the chlorine odor appears at all taps. Re-circulate the water back into the well for at least an hour. Then close the tap and stop the pump.
2) Mix two more quarts of bleach in ten gallons of water and pour this chlorine solution into the well. Allow the well to stand idle for at least 8 hours and preferably 12 to 24 hours.
3) Pump the well to waste, away from grass and shrubbery, through the storage tank and taps, such as an outside connection, until the odor of chlorine disappears. The chlorine may persist for 7 to 10 days depending on how much water is used.
After all the chlorine is pumped out, a water sample should be collected and tested by the health department, if this service in available, to determine whether all contamination has been eliminated. If the health department does not examine samples from private water supplies, a commercial laboratory will have to be used and prior arrangements make to pick up a sterile sample bottle and sampling instructions. Make sure all chlorine has been pumped out of well (no chlorine taste or odor in the water) before a sample is collected.
Proper disinfection of flowing wells or springs requires special treatment, which the health department will explain in specific instances.
Remember that disinfection is no assurance that water entering the well or spring is free of pollution.