Guide for Private Water Systems Only

HOW DO I DISINFECT MY WELL?

1. Draw off a small supply of drinking water for overnight use before disinfecting the well.  See "Emergency Water Treatment" procedures for this overnight supply.

2. Determine the depth of your well.  Mix the amount of liquid bleach, as described below, with several liters (10 to 20 litres) of water.  Use common, unscented household bleach that does not contain detergent or other additives such as fabric-guard.  Always follow the directions on the bottle label for safe storage, handling and use.  Chlorine should always be used in well-ventilated places because breathing the fumes is dangerous.

The amount of chlorine required for a dug well ( 3' diameter) is approximately 2 cups (500 mLs) of bleach per tile of water.

The amount of chlorine required for a drilled well (6" diameter) is approximately 2 cups (500 mLs) of bleach per 50 feet of water.

Newly constructed wells may require stronger treatment (consult the well installer).  Typically, new wells require a chlorine concentration of 250 mg/L or parts per million (ppm) whereas existing wells require 50 ppm chlorine for effective disinfection.  

3. Remove the well cap and examine the well.  Prior to adding the chlorine solution, the sides of the well should be cleaned – this is an optional process however it should make the overall disinfection of the well more effective.  Consult with a licensed well technician / driller if you are unsure of how to proceed with cleaning to avoid damaging the well or well equipment. 

In the case of large diameter wells such as dug wells, all floating debris should be removed and the casing/cribbing washed and scrubbed.  Check to see that the tiles are sealed and that there are no leak stains where the tiles join together.  Dug well tiles can be sealed with a suitable hydraulic cement – check with local plumbing and hardware stores.  Scrub the sides of the well with a clean/new mop and chlorinated water.  Remove all sludge that has accumulated at the bottom as bacteria will likely be present in the sludge.  Since many bacteria are motile, meaning they have the ability to swim, they can escape the sludge and travel back and forth in a water column and in plumbing.  In 5 – 6 “ drilled wells, pumping equipment would have to be removed before cleaning.  After the cleaning the pump could be reinstalled and the well pumped until the water is clear. 

4. Pour the mixed chlorine solution into the well.  If the well is buried, either expose the top of the well, remove the well seal and pour the solution directly into the well, OR pour the solution through a clean funnel into the air vent or siphon through the vent (flush the air line with clean water after chlorination).  Note:  Wells should be above ground.  If you have a buried well, consider adding an extension to raise the well 1 to 2 feet above ground.

5. If you have a carbon or charcoal filter, remove it from your system (after bleaching the system, replace with a new carbon or charcoal filter).  If you have a water softener or other treatment equipment, check with your water treatment dealer about whether disinfection may adversely affect your treatment unit.  It is possible for water treatment equipment to become fouled and lines into and away from equipment should be disinfected.

6. Start the pump and bleed air from the pressure tank.  

7. Open one faucet in house and let the water run until you can smell the chlorine.  Turn the faucet off.  Repeat this procedure with all hot and cold faucets.  This may take awhile for deep wells.  Be sure to include all inside and outside faucets, cold and hot water, dishwashers, toilets, baths, showers etc.  The principle is to have disinfectant in every plumbing line in the house as well as disinfectant in the well.

Chlorine is a very reactive substance.  When added to the well it will first combine with organic and inorganic substances such as iron, hydrogen sulfide and algae.  There is no disinfection at this point.  After the demand of these compounds has been met, then the residual chlorine begins the disinfection process.  If there is no smell of chlorine coming through or the smell is faint, then more chlorine may have to be added to the well to achieve adequate disinfection. 

If you are having trouble getting the chlorine down to the pump level, hook one end of a garden hose to an outside tap and insert the other end into the top of the well.  Turn on the outside tap until you smell the bleach coming through the other end.  This helps to re-circulate the water and drive the chlorine down to the pump.  Once you smell the chlorine coming from the garden hose, shut off the outside tap and proceed with opening all of the taps, hot and cold, in the house.  Turn off the taps once you smell the bleach coming through.

8. Seal the top of the well.  Let the system sit for a minimum of 6 hours or preferably overnight.  Do not leave chlorine in the system for more than 24 hours as it may affect some pump parts. 

9. After the 6 to 12 hours, flush the well using an outside tap until the chlorine odor has completely disappeared.  (Using an outside tap prevents a large amount of bleach from entering the septic tank that could kill the good bacteria working in the tank).  Afterwards, flush the lines of the house also. 

Note:  As chlorine comes in contact with dissolved iron in water, the iron will precipitate out as rust and the water will turn a yellow color.  Other staining and sedimentation problems may occur.  If this is the case with your water, remove the screens from the faucets before flushing the lines.  This problem should clear up with time and flushing.  It may take a few days.  In the meantime, do not use this water for aquariums or pets.  Check with your physician about other uses of the water, such as bathing, if you have allergies or other medical concerns.

Note:  Do not flush the water into a natural body such as a lake, stream or creek; avoid flushing into gardens.  

10. Wait one to five days before collecting a sample for bacteriological testing.  There should be no chlorine odor remaining at the time of sampling.  Boil or chlorinate all drinking water, or use an alternate source, until you receive a satisfactory laboratory report.

11. If the results come back with NO detectable bacteria then:

a) After one to two weeks, sample again to ensure that the well is not recharging with contaminated water.  Two consecutive “safe” tests, performed on samples obtained over a period of one to three weeks, will probably indicate that the treatment has been effective.

b) Sample regularly 2 to 4 times a year to ensure the water supply has remained secure.

Note:  In Ontario, samples can be submitted to the local Public Health Unit for testing of bacteria at little or no charge for private residents; verify with your local Health Unit.   

    If the results come back WITH bacteria then:

a) Contact a licensed well technician to inspect your water system.

If the source of contamination cannot be found and eliminated, the water should subsequently receive continuous disinfection.

HOW DO I PERFORM EMERGENCY WATER TREATMENT?

BOIL the water for 5 minutes.  After it has cooled pour the water repeatedly from one container to another to eliminate the flat taste.
CHLORINATE the water by adding 1/4 teaspoon of bleach to 1 gallon (4.5 Liters) of water.  Mix well and allow to stand for 15 minutes. 
BOTTLED WATER may be purchased as a temporary alternate to treating the water supply.

HOW CAN I BE ASSURED A SAFE WATER SUPPLY?

1. Properly site and locate new wells.  The well itself should not be located downhill form any source of pollution.
2. Ensure your well is properly constructed and located to prevent the direct entry of surface water.
a) The well should have a secure lid with no cracks and should seal tightly.
b) Direct contaminated water away from the well – such as from tile drains, livestock operation and roof eaves.
c) The ground should slope away from the well directing surface drainage away from the well casing/tiles.
d) Vegetation should be allowed to grow up around the well.  Avoid gardening and fertilizing next to the well.
e) Construct a small fence to keep animals off of and away from the well.
f) Ensure that tiles for dug wells (usually three foot diameter cement) are sealed at the joints.
3. Inspect pumps and pipes on a regular basis. 
4. Take 2-4 seasonal bacteriological water samples from your house and cottage (especially spring after snow-melt and fall after the rainy season) even if you have a water treatment system.
5. Take a bacteriological water sample if your well has been subjected to flooding.
6. Always take a bacteriological water sample from a newly constructed or renovated well.
7. Take a bacteriological water sample when there have been plumbing alterations to your water system (e.g installation of new plumbing lines, installation of a water treatment system).
8.  Take a bacteriological water sample if there is a noticeable change to your water e.g. odor, clarity, taste or color; or if there has been a change in the surrounding land use.  Note however that there may be slight natural variation to some characteristics e.g. intermittent sulfur smell from water from a drilled well.

WHAT KIND OF A WATER TREATMENT SYSTEM WILL BE EFFECTIVE AGAINST BACTERIA?

Be sure to consult with a reputable water system dealer when considering treatment
Ultra Violet -- An ultra violet (UV) lamp should be sized according to the volume and flow rate of water that requires treatment.  There must be a fiber or sedimentation filter installed prior to the UV lamp.  This filter traps particles that bacteria might otherwise "hide behind" when passing by the UV lamp.  UV lamps must be left on continually as some bacteria are swimmers and may travel up a water line even when water is not being drawn through the line.  The lamps should also be equipped with some kind of visual or audible warning system to indicate when bulb replacement is required.  Note that UV may not be effective against some organisms such as iron bacteria and parasite cysts.  Also, highly mineralized ground water and/or organisms that coat surfaces, may prevent the UV from working as effectively as required.
Chlorine Injection -- In this type of system, chlorine is injected directly into the water.  There is a retention tank allowing time for the chlorine to interact with the water.  A filter follows the tank trapping any particulate e.g. iron oxide (rust) that is formed when iron reacts with chlorine.  A charcoal filter can also be installed after the chlorinating system to remove the taste of chlorine.  (Note that a charcoal filter on its own without any other treatment component is not designed to remove bacteria, rather it can become a breeding ground for such organisms.)
Distillation -- Water is converted to steam at 100 oC and "boiled over" into a reservoir killing bacteria and leaving impurities behind.  Although effective, some distillers may be slower to produce volumes of treated water compared to other types of treatment systems.  The reservoir should be cleaned and disinfected according to manufacturer's instructions and periodically tested.
Some parasites (often in cyst form) must be physically removed from water by means of filtering e.g. ceramic filter with a pore size of less than 5 microns and sometimes less than 1 micron.  Generally, as pore size is reduced, the rate at which water is filtered is also reduced.   
There may be other systems available for treating bacteria.  Consult with several treatment dealers to obtain various options, after-installation service packages and prices.

WHERE DO BACTERIA COME FROM?

Some types of coliform bacteria naturally live in the first several feet of soil and that is why it is important to prevent surface water from entering a well.  Also, when any maintenance has been done to a plumbing system or well, or a new well has been installed, bacteria may come from mechanical components or busy hands at work.  In the kitchen, bacteria can be deposited on the end of a faucet if the faucet is wiped with a contaminated dish cloth.  Bacteria are sometimes found on the end of faucets in bathrooms and laundry rooms.  It is recommended to remove the screen from a faucet and flame the end of the faucet with a match or a lighter prior to running the water to collect a sample.  This prevents bias of contamination coming from a dirty faucet rather than the water supply. 

HOW ARE WATER SAMPLES TESTED FOR BACTERIA?

There are a couple of different methods to test for bacteria.  At Near North Laboratories Inc., a widely used method known as membrane filtration is the primary method of identifying bacteria in drinking water.  For this test, 100 mL of water is filtered and the filter is placed on an agar (similar to gelatin) within a petri dish (a small round plastic dish with a lid).  The agar contains nutrients that will promote bacterial growth.  The plate with the filter is placed in an incubator for 22 to 26 hours at a specific temperature to promote optimum bacterial growth.  During that time, a single bacterium will multiply enough times to be visible as a colony.  The colonies of bacteria are counted as CFU or Colony Forming Units and are reported per 100 mL of sample.  Different types of dyes are used in the agars that allow different kinds of bacteria to grow with specific colors.  For example, only E. coli bacteria will turn blue on DC agar and that is how they are identified.

SURFACE WATER

Surface water supplies are obtained from lakes, streams, ponds and rivers.  These supplies are always subject to intermittent pollution and should therefore be continuously checked and treated to make them safe.  Other than water-borne bacteria, other organisms such as algae and parasites can render drinking water from surface water supplies unfit to consume.  Most Health and Environment officials maintain that all drinking water from unprotected surface sources should be disinfected by some method.

WELL WATER

Ground water supplies include dug, bored, driven and drilled wells and if properly maintained, they are normally a resource of safe water, providing there is no source of pollution nearby.

DUG WELLS

A dug well is normally 0.9 meters (3 feet) in diameter and 4.5 m to 11 m (15 to 36 feet) in depth, depending upon where the ground water table is encountered.  Soils, penetrated with ground water, are usually penetrated only for a short distance and therefore after considerable heavy water usage or during a drought, the dug well might run dry.
Dug wells are generally more susceptible to surface water contamination than drilled wells, especially older wells that were not constructed with watertight concrete casings as recommended.  Old dug wells that are lined with stone or brick walls should be reconstructed so that their upper 2.5 m (8 feet) are set with water-tight joints.  There are clay products available that can be used to seal well tiles together and will cure under water.  These products are usually available from suppliers of water well equipment, plumbing and hardware stores.  Wells should be capped off with water-tight tops that do not have cracks or unsealed openings in them.

TO INSPECT A DUG WELL

To inspect the inside of a dug well, remove the lid of the well.  Check for anything floating on top of the water and remove if necessary.  Check for drip stains on the inside walls especially below the joints of the tiles.  Staining may indicate that surface water is entering the side of the well.  Scrub the walls of the well with a dilution of household bleach.  Reseal the tiles if necessary using a clay that will cure under water.

DRILLED WELLS

Drilled wells are generally less likely to become contaminated with bacteria. Drilled wells serving single households are usually 10 - 15 cm (4 - 6 inches) in diameter and commonly between 15 to 60 m (50 to 200 feet) in depth, depending on the availability of water.  Contamination of drilled wells usually occurs by surface water entering through the top of the well casing, a crack in the casing or a shift of the casing next to the bedrock.  The caps for drilled wells should be provided with a seal that generally consists of a rubber disk sandwiched between two metal plates.  The seal is designed to accommodate pump pipes and an air vent.  The air vent should never be sealed over.  When bolted in place the steel plates squeeze the rubber disk outwards against the casing to provide a water-tight seal.  Water taken from drilled wells generally is more highly mineralized.  Nuisance bacteria such as iron or sulfur bacteria can reside in deep drilled wells.  Nuisance bacteria may or may not cause any health effects, however proliferation of nuisance bacteria can cause plugging of filters and biofouling of plumbing lines.

NEAR NORTH LABORATORIES INC.

The company has been testing for the presence of bacteria in drinking water for 15 years.  The company is accredited by the Standards Council of Canada (SCC) through the Canadian Association for Environmental Analytical Laboratories (CAEAL) and licensed by the Ontario Ministry of Environment (MOE) for the analyses of Total Coliform, E. coli, Fecal Coliform, Background (from the Coliform plate) and Heterotrophic Plate Count.  In Ontario, the fecal coliform that is generally used for regulating drinking water supplies is E. coli. 
As well as microbiological testing, the laboratory performs chemical and physical tests on water (to both drinking and surface water criteria), wastewater and soils.  Specific concerns such as lead in paint can be assessed.  The company provides air sampling for mould, noise, odors and asbestos as well as product development and treatability studies.
The lab is located in North Bay, which is at the crossroads of Highways 11 and 17.  The address is 191 Booth Rd. Unit 11.  Office hours are from 8:30 am to 5:00 pm Monday to Friday; other times by appointment only.  Phone (705) 497-0550; Fax (705) 497-0549; email:  This e-mail address is being protected from spam bots, you need JavaScript enabled to view it    
FURTHER INFORMATION

There are a variety of sources for additional information including:

Ontario Ministry of the Environment (usually have free publications and fact sheets regarding wells)
Ontario Ministry of Health
Health and Welfare Canada
Local Library
Internet
Well Installation Companies
Water Treatment Dealers

The above information is provided to assist you with your drinking water needs.  This information should never be substituted for the advice provided by medical, environmental or health officials.  Although the information, to the best of our knowledge, is correct, Near North Laboratories Inc. accepts no liability for omissions, misprints, misinterpretation or personal injury as a result of this publication.

REFERENCES

Health Canada:  Water Talk, “What’s in Your Well? – A Guide to Well Water Treatment and Maintenance”, June 25, 2003.

Nova Scotia Environment and Labour, “Disinfection of Water Wells by Chlorination”

Township of Malahide, Ontario, “Well Dinsinfection”

Prince Edward Island Fisheries, Aquaculture and Environment:  Water Resources Division, “Well Disinfection”, April 2000

Lifewater, Section 15, “Well Disinfection” @ www.lifewater.ca

Corporation of the Town of Georgina, “Private Water Wells Sampling Procedures”  March 23, 2004

Canadian Ground Water Association in collaboration with the Red Deer College:  Fact Sheet #4 “Guidelines for Sanitizing a Water Well”