Drinking water advisory (DWA)

A drinking water advisory is issued by the Medical Officer of Health when the public’s water source is not safe. It is a preventative measure put in place to protect the health of the public from drinking water that may be contaminated.

Why is a drinking water advisory issued?

A drinking water advisory is issued when:

• The Ontario Drinking Water Standards are not met.
• Conditions exists that cannot be corrected by boiling or disinfecting the water.

The extent of restriction on water use depends on the situation and the reason for issuing the advisory. Always follow Public Health’s recommendations on water use.

What is the difference between a boil water advisory and a drinking water advisory?

A drinking water advisory is issued when a condition exists in a drinking water supply that cannot be corrected by boiling or disinfecting the water. This condition may result in a risk to consumers. A boil water advisory is issued when a condition exists that can be corrected by boiling the water before consuming it.

Can you use the water when a drinking water advisory has been issued?

You can use the water for laundry and bathing (excluding small children), but the water should not be used for:

• drinking
• making juice
• making infant formula
• making ice
• cooking
• washing fruit and vegetables
• brushing teeth

For these purposes listed above, water from an alternate source, such as bottled water should be used.

Are babies receiving breast milk at risk?

Breastfeeding is important. Continue to breastfeed your child. If a mother has been drinking water that may have been affected, it is only in very rare circumstances that breast milk may be contaminated. If there is an issue, Public Health will notify local residents through media channels.

Are babies receiving infant formula at risk?

Infant formula should be used after making an informed decision. During the advisory do not use tap water to prepare the formula. If you have refrigerated prepared infant formula or boiled water, it should be discarded. For these purposes, water from an alternate source, such as bottled water should be used. Like tap water, all water from alternative sources must be brought to a rolling boil for at least 2 minutes before being used for formula.

Where can you get water?

Bottled water can be purchased from local suppliers such as grocery stores, convenience stores, and department stores. In many cases, the municipality will provide residents with stations where they can obtain larger quantities of water.

How can you disinfect a container for storing drinking water during a DWA?

1. Use a container that has only been used for water or food. Clean the container with hot soapy water.
2. Rinse the container with clean water from an alternate source not affected by the DWA.
3. Disinfect your container by mixing 50 ml of household bleach with 5L of water from an alternate source not affected by the DWA.
4. Shake the container for at least 1 minute.
5. Use the same solution to disinfect the cap, lid, and mouth of the container.
6. Empty the container and let air dry.
7. Replace the lid.

Protect the container from re-contamination:

• Avoid touching the mouth, cap, or lid of the container.
• Keep the container away from surfaces such as floors.
• Replace the lid as necessary.
• Before re-filling with drinking water from an alternate source, clean and disinfect the container as described above.

Can you use the water for handwashing?

Hands should be washed using potable water obtained from an alternative source. Alternatively, you can use alcohol-based hand sanitizers, containing more than 60% alcohol. These products are widely used in the health care setting after washing hands or in situations when water is not available. If hands are not visibly soiled alcohol based hand sanitizers alone are sufficient.

However if the hands are visibly soiled a pre-moistened towelette, such as those used for cleaning babies during a diaper change, can be used to remove the dirt then use the alcohol-based hand sanitizer to kill bacteria.

Can you use the water to take a bath or shower?

Normally adults and teens may shower with untreated water as long as no water is swallowed. Older children could also be given a shower with a hand-held showerhead, avoiding the face. Younger children should be sponge-bathed instead of bathed in a tub because they may swallow tub water. If there is an issue where bathing should not be done, Public Health will notify local residents through media channels.

Can you use tap water to fill wading pools for children during a drinking water advisory?

No. Tap water is not safe to use in wading pools because small children may get potentially contaminated water in their mouth, which could adversely affect their health.

Can you wash your dishes?

You should not wash your dishes with the water from your home until after the drinking water advisory has been lifted. If possible, use disposable dishware and utensils, or use water from an alternate source.

Can you do laundry?

Yes, but you should be aware that tap water may discolour your clothing.

What should you do during a drinking water advisory if your doctor has told you that you are immunocompromised?

Always follow the advice of your health care provider or dietitian. You might be advised to use water from an alternate source, even when a drinking water advisory has not been issued.

Can you use tap water during a drinking water advisory if you have a water filtration device?

No, the water should not be used for drinking, cooking, making juice, and infant formula, making ice, washing uncooked fruit and vegetables, or brushing teeth until further notice. Use water from an alternate source for these purposes.

Are there precautions for daycare centres during a drinking water advisory?

Yes. Daycare centres should:

• Stop the use of water play tables during this time.
• Drain all water play tables or play areas containing water.
• Avoid activities/crafts which use water or where there is a risk that children may consume a product containing the water (for example, hand painting, baking, pasting with glue made from flour and water).

When does the Medical Officer of Health lift a drinking water advisory?

The Ontario Drinking Water Standards (e-Laws Ontario) state that the Medical Officer of Health should continue the drinking water advisory until 2 consecutive sets of samples taken from all parts of the water system show that the standards have been met.

What should you do when the drinking water advisory has been lifted?

If you use the municipal water supply, you should run each of your cold water taps for at least 5 minutes or until the water runs clear. Large-volume users (for example, hospitals, schools) may need to run cold water taps for a longer period of time on first use. To get rid of sediment, screens should be removed, rinsed and replaced.

Should you expect anything different with your water after a drinking water advisory has been lifted?

It is possible that you might detect a slight taste of chlorine during the first use. The municipality may have been using a higher level of chlorination.

What if you see or taste something unusual in your water after a drinking water advisory has been lifted?

If you have any concerns, call your local municipal office.

Do you need to test your water if you are on a municipal water supply after a drinking water advisory has been lifted?

No, you do not need to have your water tested if you are on a municipal water supply. Do not take municipal water samples to Public Health for testing. The municipal water supply is tested and monitored regularly by the municipality.

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This item was last modified on April 19, 2024