Procedures for Well Disinfection

PROCEDURES FOR WELL DISINFECTION

NOTE: READ THIS ENTIRE PROCEDURE BEFORE PROCEEDING

If you are unsure of any of the following steps, please call the Environmental Engineering/Policy Program at 301-883-7681, weekdays between 7:30 a.m. and 4:00 p.m., or seek the assistance of a licensed well driller or licensed pump installer.

Materials needed to complete this process:

plastic buckets filled with water
Measuring cup
Clean garden hose that will reach to the top of the well
a spray nozzle
one gallon of unscented common household laundry bleach (any variety)

CAUTION - Do not leave bleach jugs within reach of children - ingestion of bleach is the most common toxic exposure for children in the U.S.

. Step 1.   Obtain and store enough drinking water to supply your household needs for at least 24 hours. (If your well is contaminated, the drinking water should be obtained from another source).

Step 2.   Switch water treatment equipment, softeners (i.e. iron removal or water conditioning equipment), or filters (if applicable) to “Bypass”. DO NOT chlorinate activated charcoal or carbon filters. These filters will adsorb the chlorine, greatly reducing the life of the filter. Water softening systems can also be damaged by excessive chlorine, and will be chlorinated separately at the end of the process. (If you are unsure about this procedure, please contact the equipment manufacturer.)

EXTREME CAUTION is advised, as you will be working with electricity and water. Potentially lethal voltages exist - if you are not acquainted with working with electricity, seek professional advice.

Step 3.   Electrical Safety: Turn off electrical power to the well pump.

Step 4.   Remove well cap: With the electrical power off, remove the cap and lift/pull the wires/wire nuts to the side to provide access into the well.

Step 5.   Mixing a chlorine solution:

CAUTION: Chlorinating products must be handled in accordance with the manufacturer's directions. Failure to follow instructions could cause bodily injury.
Wear old clothing that will protect you from accidental skin contact (long sleeve shirt and pants, socks and shoes, and gloves). Goggles should be worn to protect the eyes. Chlorine should always be mixed in a well-ventilated area because breathing the fumes can be hazardous to your health. Take safety precautions while you are handling bleach to protect yourself from splashing and fumes. If the bleach gets on your skin, flush the area immediately with clean water.

Note: Concentrated bleach will injure grass or other plant life. If you are mixing the chlorine solution on grass, you may wish to place a tarp or some other material down first. You may also wish to cover plants located adjacent to the well during the chlorination process.

The amount of chlorine bleach necessary to adequately disinfect your particular well can best be determined based on the depth of your well. In general, the depth of the well is dependent on the location of your property within the County. If you live North of Route 50, use 1/2 gal of bleach; South of Route 50 and North of Route 4, use 1 gallon of bleach; and South of Route 4, use 1 1/4 gallons of bleach.
Thoroughly mix the proper amount of chlorine bleach as determined above with about 4 ½ gallons of water in a non-metallic container. Allow an additional pint of bleach to the mixture for each 50 gallons of well pressure tank capacity. The safest way to be sure that the amount of chlorine added is sufficient is to add a little more than is recommended. However, just a little more, as much more is not necessarily much better.

NOTE: If you have a dug well with a diameter greater than 18 inches, use 2 to 4 gallons of bleach added directly to the well, without dilution. Be advised that many dug wells are difficult or impossible to disinfect due to their unsanitary construction.

Step 6.    Adding chlorine to the well - The metal top of the pitless adapter connection for the water line from the well to the house will be visible about three feet down into the well. Pour the chlorine bleach mixture directly into the well while avoiding pouring the solution onto the pump wire connections; that is, pour between the pipes inside the well and the well casing, gently washing down the sides of the casing and drop pipe in the process. Turn the power back on to the well pump. Turn on the water to the hose completely; let the hose run into the top of the well long enough to detect a strong chlorine smell from the end of the hose. This may take between 10 minutes and an hour, depending on the size of your household plumbing system. (You may notice that the water coming from the garden hose turns reddish for a brief period. This is due to the chlorine precipitating iron in the water. If the water appears excessively red and cloudy from this reaction, discharge the hose outside of the casing until the water runs clear.) Once you detect the chlorine smell, attach a spray nozzle to the end of the garden hose and then, thoroughly wash down all the visible surfaces inside the well for about 10 minutes.

Step 7.    Recirculating chlorinated water - Remove the hose spray nozzle and put about 5 feet of hose down into the well to assure that it doesn’t fall out, and let this chlorinated water run into the well for about two hours. This will create a loop from the house to the well that will re-circulate water into the well, ensuring complete mixture of the chlorine solution. After two hours, remove the hose and securely replace the well cap.

NOTE: For wells with any history of adequate supply problems, it is recommended this re-circulation process be conducted intermittently, allowing the well to “recover” in between cycles, e.g. 30 minutes on, 60 minutes off over a five hour period, to ensure that the well does not run dry and damage the pump.

Step 8.    Bringing chlorinated water to each faucet or fixture - While the chlorinated water is still circulating, run water from each fixture inside the house for at least one minute, or until you smell the chlorine odor. (This will ensure the chlorinated water from the well has been distributed throughout the household plumbing.) Start with the highest fixture in the house (usually a showerhead in an upstairs bathroom). Let the hot water run first until the chlorine smell is detected, then do the same with the cold water. As soon as you smell the chlorine bleach from both the hot and cold supplies to a tap, turn it off and move on to the next one. (If you cannot smell bleach from a particular faucet or fixture after five minutes, repeat steps 5-8.) Repeat this procedure for every faucet/fixture in the house, including all cold and hot water taps, toilets (flush each once), showers, bathtubs, dishwasher, washing machine, outside faucets and hydrants. Fill the dishwasher and run it. If you have an automatic icemaker, empty it and make a new batch of ice. This gets chlorine into that part of the system. Go to your laundry area and run a large sized load of white laundry in warm water. (Be sure there are no colors in this because this is real bleach, not the color-safe variety!) Be sure to run the cold and hot water in the laundry sink. If you have more than one garden hose faucet, run water through them all. Look around, have you run water out of every place that you can? If the answer is yes, you have completed half the job. Leaving even one line out of the chlorination procedure may lead to inadequate disinfection, which may result in the need to repeat the entire process. Now the water must not be used for drinking, bathing or cooking for 12-24 hours.

CAUTION: Do not leave the concentrated chlorinated water standing in the well for more than 24 hours as this may affect the well pump.

You may flush the toilets, but try to minimize the number of flushes. It is helpful to post reminders on the faucets, reminding members of your household not to use them.

NOTE: Do not drink well water containing high levels of chlorine. Do not shower/bathe with water containing high levels of chlorine due to the possibility of damaging your eyes.

Step 9.   Flushing out the chlorinated water - Large volumes of the chlorinated water must not be run into the sewage disposal system. Therefore, the chlorinated water should be flushed out of the household plumbing through an outside spigot and garden hose. Reattach your garden hose and take the open end to a place in the yard where you can run the water out onto the ground and it will not run over your sewage absorption area (septic drainfield), your neighbor’s absorption area or form a puddle on the neighbor’s property. Leave the hose running until you can’t smell the chlorine anymore. When running off the chlorinated water, discharge away from grass, shrubs and other landscaped areas that could be damaged by the concentrated chlorine. Also, be careful not to discharge into any stream, surface water, storm drain or gutter that could ultimately damage aquatic life downstream.

After the chlorine smell has dissipated, go into the house and run another large sized load of white laundry in warm water. If you don’t have any white things to wash, just run the machine through a warm water wash cycle. (This is not a waste of water; you need to clear the chlorinated water out of the system.) Turn on the indoor faucets, starting with the shower in the farthest and highest bathroom, and allow each to run until the chlorine smell dissipates there also. Flush all of the toilets once. This de-chlorination process may take as little as a few hours or as much as four days to completely remove the chlorine odor from the water system. This is dependent upon many factors including the height of the water column in the well casing, well drawdown, pump capacity, etc. Wait about an hour and then run the water again to make sure no chlorine odor remains. Your water supply must be completely free of chlorine before it is re-tested.

NOTE: The Health Department and private labs will not analyze water samples that contain chlorine.

Step 10. Water “Softener” disinfection - Water treatment equipment, e.g. water softeners, filters etc., may be damaged by excessive amounts of chlorine, so we “Bypassed” these units in Step 2, but the softener itself should also be chlorinated when there are bacteria problems. Follow the manufacturer’s instructions or use the following procedure: add ½ cup of bleach to the brine tank, and regenerate the unit as normal. Be sure to return the bypass valve to flow through after regeneration.

Step 11. Resample the well - Contact your Health Department Environmental Health Specialist (301-883-7681) or a licensed private laboratory for resampling. Use your water normally except for drinking and cooking purposes. You should always have your well water retested after chlorination, and before using it for drinking or cooking purposes. Until tested and found potable, bring the water to a rolling boil for at least one minute before consuming or using for food preparation.

NOTE: It is not unusual to require several disinfections to clear your water supply of coliform bacteria that have been growing in the system for a period of time. If the well fails to test free of bacteria, contact the Health Department’s Environmental Engineering Policy/Program at 301-883-7681 to discuss options, including enlisting a licensed well driller to utilize special techniques and equipment to flush the well system.