Pathogens and Your Well Water
What's in your well's water, besides water?
Only test results that are carried out by the public health laboratory or a private laboratory can tell you for sure.
More about E. coli
When you submit your well water to the public health laboratory or a private laboratory for testing, it will be analyzed for the presence of “pathogens.” Pathogens are organisms that cause illness in humans. When it comes to well water, pathogens of concern include certain forms of bacteria, protozoa and viruses. While each of these organisms can lead to different illnesses of varying severity, there are some very unpleasant symptoms common to many, including diarrhoea, nausea, abdominal cramps and low-grade fevers.
Here's the take-home message: your well is your first line of defence against harmful organisms reaching your water supply. Maintain your well regularly and thoroughly – it's easier to prevent problems than to fix them. To complete your well water safety routine, get your water tested regularly.
Three uninvited guests: bacteria, protozoa, and viruses
Bacteria are a natural part of life. In fact, there are many forms and functions of bacteria we couldn't live without, such as those that break down organic matter (e.g., food waste, leaves). Water is a preferred environment for bacteria because their membranes could otherwise dry out. But some bacteria in water can lead to serious illness or disease, such as gastroenteritis or salmonellosis. These days, E. coli O157:H7 is probably the most infamous disease causing bacteria.
Some protozoa can live in animals and humans, and are passed in feces. These tiny parasites are able to survive in surface water for long periods of time as dormant cysts. Some waterborne protozoa can cause illness, such as giardiasis or cryptosporidiosis. Viruses reproduce by infecting living cells. Some viruses found in water cause illness, including Hepatitis A and the Norwalk virus.
Protozoa and viruses are usually found only in surface water that has been contaminated by animal or human feces. However, groundwater can become contaminated through contact with surface water. In other words, if surface water can penetrate any unsealed joint or crack anywhere in your well, your water is at risk.
The most harmful pathogen is Escherichia coli (or E. coli) O157:H7. It's spread through contaminated food (such as undercooked hamburger) and water. Symptoms may include stomach cramps, vomiting, fever and diarrhoea. Severe cases can progress to kidney failure in the elderly and children. Early symptoms are common to a number of diseases, and may or may not be the result of contaminated drinking water. Contact your doctor for more information.
Although E. coli O157:H7 can cause serious illness, most of the other hundreds of E. coli strains are harmless, and some are even beneficial. In fact, E. coli make up part of the natural flora – bacteria that live in your large intestines.
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How pathogens move through and survive in soil
As described in Get Acquainted with Your Well , when surface water travels down through soil to groundwater, it can take harmful pathogens with it. Fortunately, soils can have a cleansing effect on harmful pathogens. But if they are able to bypass soils' natural cleansing action, pathogens can survive. Bypass routes can introduce human and animal wastes into groundwater by reducing the time and distance it takes to travel through soils. The shorter the travel time, the greater the risk of contamination.
Have you built an expressway for pathogens?
Some of the facilities or activities on your property might be providing pathogens with these bypass routes. A well that's poorly constructed or plugged provides one route. An onsite septic system that's improperly or poorly designed, maintained or located provides another. Weather can also create a bypass route. Very heavy rains or flooding can move contaminants through soil at faster rates than normal.
The arrows show the pathways that pathogens can follow to get into an improperly constructed, shallow well. The red shading indicates the “annular space,” which is the space outside the well casing that was created when the hole for the well was made. In this well, the annular space is unsealed at the top, and acts as a duct for contaminated surface water to pass down into the well intake at the bottom. To make matters worse, contaminated surface water can also enter the well through unsealed tile joints and cracks.
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Is your well playing host?
Get in the habit of putting your well water to the test. How do you know if your well water is playing host to unwanted organisms? Regular testing of your well water is the best way. Test your well water regularly. Three times per year – in Spring, Summer and Fall – is recommended. Routine testing also provides an early warning signal of potential problems.
Some water-testing lingo
When drinking water is tested for biological (as opposed to chemical) contamination, the bacteria that are tested for are called indicator organisms or indicator bacteria. The presence of indicators acts as an early warning signal. It tells you there are health risks with your well water. The indicator bacteria usually show up in a test if your water has become contaminated with surface water.
There are two indicator organisms that public health labs will test for when you submit a sample. These are Total coliform and E. coli.
Total coliform (or T.C.)
- are a general family of bacteria that is found in animal wastes, surface soils and vegetation
- indicate contamination of water with organisms, and possible evidence of surface water contamination in your well water
- provide an early warning signal that there may be a problem with your water supply
- are a group of bacteria that live in the intestines of warm-blooded animals
- indicate recent fecal contamination from sources such as human sewage or livestock waste
- indicate that there is a problem with your water supply
Don't use water that has tested positive for Total coliform or E. coli. Don't use it for drinking, making infant formula and juices, cooking, making ice, washing fruits or vegetables, brushing teeth, bathing or showering. And unless you've disinfected it, don't use it to wash hands.
For more information, see the Ontario Ministry of Health and Long-Term Care Web site. It's listed at the end of this Information Sheet.
If your test results show the presence of indicator organisms, take action! Everyone who drinks from your well is at risk. You must identify the source of contamination and prevent its access to your well. It's important to get the job done quickly and right; consult a well contractor or your local health unit as soon as possible.
If your results show that your drinking water meets the Ontario Drinking Water Standards, then continue to have the water tested at least three times a year. One of the three samples you send for testing should be taken in the Spring.
Sample your well water until you have three consecutive samples (collected one to three weeks apart) that meet the Ontario Drinking Water Standards of less than 5 Total coliform and no E. coli.
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Changes in your water
It's important to know the difference between water quality that could relate to health concerns (termed health parameters) and those processes in nature that only affect the appearance, smell or taste of your water (aesthetic parameters).
A change in your water's aesthetic parameters is not necessarily a health risk. However, they might signal contamination or deteriorating water quality. If you notice a change in these parameters, you should submit a water quality sample for testing as soon as possible.
If you are concerned about the potential presence of a particular contaminant, make sure the contaminant is specifically tested for.
To learn more about what's involved in having your well water tested, please see the Information Sheet, Putting Your Well Water to the Test, in this series.
For more information about long-term water treatment options, please see the Information Sheet, Choosing a Water Treatment System.
Test three times annually, and when…
In addition to regular testing, well water should be tested:
- after any repairs (such as pump repair or replacement)
- if the well has not been used for several weeks
- if there has been flooding, or
- there has been a change in water appearance, colour or odour.
And if you have one of the “highly vulnerable” water supplies described in Get Acquainted with Your Well , you may want to consider having your well water tested more frequently.
(Information adapted from Ministry of Ontario Info rmation Sheets)