What your lead test result means

The numbers on your report

Lab reports show lead in one of two units:

• mg/L: milligrams per litre
• µg/L: micrograms per litre (sometimes written ug/L)

1 mg/L is 1,000 µg/L. So 0.010 mg/L and 10 µg/L are the same amount, and 0.005 mg/L is 5 µg/L.⁠^[2][1]

How to read your report

Look for these on your lab report:

1. The lead line. It may say “Lead” or “Pb”, the chemical symbol for lead.
2. The number and its unit, mg/L or µg/L. Convert to µg/L to compare with the limits below.
3. A “<” sign, if there is one. It means “less than”. A result written “<0.0001 mg/L”, as in the City of Hamilton’s own sampling tables, was below the smallest amount the lab reports.⁠^[3]
4. The sample type, if the lab tested more than one: standing or flushed (see below).
5. The sample date and where the sample was taken.
6. For a well test, two lead lines: total lead and dissolved lead. Hamilton’s Medical Officer of Health asks some well owners to test for both (see below).⁠^[4]

The two limits

Ontario’s regulated water systems are held to the 10 µg/L standard. Health Canada’s guideline is lower.

How does Hamilton compare?

In the City of Hamilton’s 2025 community lead sampling, none of 100 homes was over Ontario’s standard of 10 µg/L.⁠^[3] The highest result was 8.6 µg/L, which is above Health Canada’s guideline of 5. Your own number tells you about your tap, which can differ from the City’s samples.

What is a safe level of lead in water?

Health Canada says no level has been identified below which lead has no effect on children’s brain development.⁠^[1] That is why it advises keeping lead as low as reasonably achievable, not just under a number.

For context, the City of Hamilton says Ontario’s limit is based on long-term exposure, and that drinking water above it for a short time does not necessarily cause a health risk.⁠^[5] The Province of Ontario says the possible effects of lead at its 10 µg/L standard are very subtle and not detectable in any one person.⁠^[2]

Children six and under, pregnant women and women planning a pregnancy are the groups the City of Hamilton names as most sensitive.⁠^[5]

Why two samples can give different numbers

How long water sat in the pipes changes the result.

• A standing sample is taken after water has sat in the plumbing for six hours or more.⁠^[2]
• A flushed sample is taken after the tap has run, in Ontario’s school and child care sampling after a 5-minute flush and a 30 to 35 minute wait.

The City of Hamilton says flushing lowers lead in tap water but may not remove it.⁠^[6] Check your lab report for which kind of sample it tested, and ask the lab if it doesn’t say.

What does a high lead level in water mean?

It means lead is reaching your tap, usually from lead pipes, solder or fixtures in the home.⁠^[6] It does not tell you where in your plumbing it comes from. What to do:

1. Contact your water utility and your local public health unit. In Hamilton: City of Hamilton, 905-546-2489, and the Safe Water Info Line, 905-546-2189.
2. Change what you drink now. The City of Hamilton advises that children six and under, pregnant women and women planning a pregnancy use a filter certified to NSF/ANSI-53 for lead, or bottled water, for drinking and for making food, juice, coffee or tea.⁠^[6] Use cold water only. See water filters for lead.
3. Find the source. Check your service line (lead pipes guide). In Hamilton, the City inspects for free and offers a loan to replace a lead line (lead pipes in Hamilton).
4. Worried about exposure? Talk to your doctor. The City of Hamilton says a blood test is the best way to know your exposure.⁠^[5]

If you’re on a well

In rural Hamilton above the Niagara Escarpment, some drilled wells have lead that comes from the bedrock, not from pipes. The City says to test those wells for total and dissolved lead, in late fall or early spring.⁠^[4]

If the lead comes from the groundwater, flushing will not get rid of it.⁠^[4] The City lists these options: bottled water, water from a known safe supplier, a reverse osmosis system, a distiller, or a filter certified to NSF/ANSI-53 for lead. See water filters for lead and well water testing.

If your result is low

A low result is good news for that tap, on that day, for that kind of sample. If your home has a lead service line, the City of Hamilton still advises replacing it as the best way to remove lead.⁠^[6]

Should you retest? We have not found a source that sets a retest schedule for homes, so ask your lab. For schools and child care centres, Ontario asks for a new sample whenever a drinking water fixture is added or replaced.⁠^[2]

Get your plan

This page explains results in general. Your plan is about your home. Send us your result with a photo of your lab report and you’ll get:

• Your number against both limits, Health Canada’s 5 and Ontario’s 10, with what it means for your household
• Next steps for your kind of home: owner, renter, apartment or well
• The help you likely qualify for, such as the City of Hamilton’s lead pipe loan and free inspection
• What to change now, while you wait

Your result is only ever shown anonymously, and we never sell your personal information. How we use your result

Haven’t tested yet? See how to test your water for lead, or start with the free check.

Sources

1. Health Canada, Guidelines for Canadian Drinking Water Quality: Guideline Technical Document, Lead. Checked November 1, 2026. ↩︎
2. Government of Ontario, Flushing and sampling for lead. Checked November 1, 2026. ↩︎
3. City of Hamilton, Corrosion Control Report 2025. Checked November 1, 2026. ↩︎
4. City of Hamilton, Naturally Occurring Lead in Bedrock. Checked November 1, 2026. ↩︎
5. City of Hamilton, Lead in Your Drinking Water. Checked November 1, 2026. ↩︎
6. City of Hamilton, Lead Water Service Replacement. Checked November 1, 2026. ↩︎