Health Information and Tools > Health A-Z >  Water Testing: Understanding your drinking water bacteria test results

Main Content

Water Testing

Understanding your drinking water bacteria test results

​​​​​​​​The Provincial Laboratory of Public Health (ProvLab) tests private drinking water systems for bacteria (total coliforms and E. coli bacteria) that may show if your water is contaminated with sewage or manure. These are called indicator bacteria. ProvLab can’t test your water for every type of harmful germ. For example, they don’t check for viruses like hepatitis or protozoa like Giardia.

Test your water at least 2 times a year. Call a public health inspector to see what’s best for your water system.

What are coliforms?

Coliforms are a group of bacteria that are almost everywhere. They are in soil, plants, sewage, and manure.

What are E. coli?

E. coli are bacteria that people and some animals have in their intestines. If your water sample has E. coli, it means your drinking water has likely been contaminated by sewage or manure.

How many water samples do I need to take?

It depends. The first sample you send to ProvLab will not tell you how many coliforms or E. coli there are or where they came from. If your first sample finds coliforms or E. coli, you will need to collect a second sample. Results from your second sample will tell you the number of total coliforms and E. coli.

Why might my sample have coliforms?

Your water sample may have coliforms if:

  • the sample wasn’t collected properly
  • surface water gets into your well, like through a cracked casing, a leaky seal, or a missing or loose well cap
  • there are problems with your plumbing system
  • your well is near a spot were water pools or near other sources of surface water

Try to find out how coliforms got into your well water. Call a public health inspector for more information.

How do I understand my test results?

Your first sample will have a result of either absent/nil or present for both total coliforms and E. coli

Abesent/nil result

  • ​Total Coliforms = absent/nil
  • E. coli = absent/nil

What it means

  • The water that was tested was satisfactory because the test did not find indicator bacteria in the water sample.
  • The water that was tested showed no evidence of being contaminated with bacteria at the time the sample was taken. The sample was only tested for coliforms and E. coli. The sample was not tested for chemicals, viruses, protozoa, or other harmful germs, and may still be unsafe to drink.
  • Results from one water sample don’t reflect the overall health risk of your private water system. You still need to monitor and treat your water properly.

Present result

  • Total Coliforms = present orE. coli = present

The result of the second sample you submit will give a number instead of just saying present.

What it means

  • The water tested was unsatisfactory because the test found coliforms or E. coli bacteria in the water sample. There may also be other harmful germs in the water sample.
  • Do not drink the water or use it to prepare food without boiling it first.

What to do

  • Review your water system and well to find out if they were built properly and if they are working correctly.
  • Make sure your well cap is on and watertight.
  • Check that the ground slopes away from your well, that there is no water pooling nearby, and that your well is away from sources of sewage and manure.
  • Collect another sample of water for testing. Make sure you follow the test instructions carefully.
  • Think about shock chlorinating your well (PDF)
  • Find out if past samples from your well also found coliforms or E. coli. If they have, your water source is more likely to be contaminated and you should think about continuous treatment.
  • Think about treating your water if it isn’t being treated already. Talk to a public health inspector or other water treatment professional.
  • Send another water sample to be tested for bacteria after you install a treatment system or shock chlorinate your well. This will make sure the bacteria are gone. A public health inspector will contact you with the results of this test.

What if I sent a sample, but it wasn’t tested?

Your water sample may not have been tested if the:

  • requisition form wasn’t completed properly (follow the instructions on the back of the form)
  • date and time were not correct on the requisition form
  • ID number label wasn’t on the sample bottle
  • sample didn’t reach the lab within 24 hours of being collected

If your sample wasn't tested, you will find the reason why near the bottom of your report.

Does it matter where my drinking water comes from (water source)?

Drinking water that’s contaminated with bacteria, viruses, or other germs can make you sick. You can get sick if you drink contaminated water or use it to prepare food, wash fruits and vegetables, or brush your teeth. You can’t see germs in water, but they can still make you sick.

Water from surface sources is not safe to drink. Sewage and manure can get into surface water sources easily, which can contaminate the water. Surface water includes water that comes from:

  • canals
  • dugouts
  • rivers
  • lakes
  • springs
  • wells near rivers or lakes
  • shallow wells (less than 50 feet)

Water from surface needs to be filtered to remove cysts (like Cryptosporidium and Giardia) and then disinfected to control bacteria and viruses. To do this, use a:

  • filter that meets NSF Standard 53, which is approved to remove cysts that cause illness, and has a pore size of 1 micron or less (absolute 1 micron)
  • chlorination system or a Class A ultraviolet light system that meets NSF Standard 55

After you install a system, test your water to make sure the system is working.

Deeper wells (more than 50 feet deep and 300 feet from a river or lake) are usually safer than shallow wells because your water is less likely to be contaminated with manure or sewage.

How do I inspect my well?

Inspect all wells (shallow and deep) 2 times a year, like in the spring and in the fall, to make sure the well head is in good condition. This can prevent surface water from contaminating ground water.

People oftern forget to take care of their private water wells. If your well is in poor condition, your water might not be safe. To check the condition of your well, check closely that:

  • your well is fully accessible
  • the sanitary seal or well cap is in place and is watertight
  • the well cap is at least 30 cm above the surface and isn’t buried
  • the air vent is screened and isn’t blocked
  • there are no cracks or openings in the well casing that could let in water, debris, or pests
  • surface water runoff flows away from your well and doesn’t collect or pool close by
  • your well is located away from any sources of pollution like sewage, manure, or fuel storage

Take time to look at your water system closely so you can find any problems with your well early. This may prevent other more expensive maintenance or repairs. It also keeps your family safe and healthy.

Don’t drink untreated surface water—it isn’t safe.

If you have any questions about water, contact Alberta Health Services Environmental Public Health​.​

Current as of: November 19, 2021

Author: Environmental Public Health, Alberta Health Services