Lead pipes in older homes: how to spot a lead service line, and why partial replacement backfires

Plumbing renovations in older houses often stop at the basement wall. The pipe beyond it, the service line from the street, may be the biggest source of lead in the house's water, and it is the part nobody looks at. Health Canada's Water Talk page covers what to check and what to do.

Where lead comes from

Health Canada says the most significant source of lead in drinking water is likely to be lead service lines. Solder, faucets and valves may also contain lead. Lead is more likely in older homes: the National Plumbing Code considered lead an acceptable material for pipes bringing water to homes until 1975. Health Canada's guideline for lead in drinking water is 0.005 mg/L, lowered from 0.01 mg/L.

How to spot a lead service line

Ask your plumber, water utility or municipality. You can also look at the service line where it enters the house, often in the basement near the water meter. Health Canada says it may be lead if it is greyish-black, or soft and easily dented when scraped with a knife. If you suspect lead, ask whether your municipality has a sampling program or will test on request, or contact your local public health authority.

Reduce exposure now

Use only cold tap water for drinking, cooking and baby formula, because hot water increases the release of lead from plumbing. After water has sat in the pipes for a few hours, flush by running the tap for about a minute, or by flushing a toilet, showering or starting laundry. Treatment devices certified to the NSF standard for lead removal, such as carbon-based, reverse osmosis or distillation units, can be installed at the main drinking tap and must be maintained, but Health Canada says they are not permanent solutions. Bathing and showering are considered safe.

Partial replacement can backfire

The permanent fix is replacing lead service lines and interior lead pipes or fittings. Usually the municipality is responsible up to the curb and the homeowner for the curb-to-house portion; some municipalities offer programs to replace both together. Health Canada warns that when only part of a line is replaced, lead particles may detach from the remaining lead pipe for 2 to 3 months, so keep reducing exposure during that time. Replacing only the city side, or only the house side, leaves lead in the system.

During a plumbing renovation

When plumbing is upgraded, Health Canada says to replace lead pipes, fittings and faucets with certified materials and use lead-free solder. Ask the plumber to identify the service line material before quoting, and to tell you if any lead remains. A renovation that adds new fixtures but leaves a lead service line in place has not solved the main source.

Prevention Checklist

• Check the service line material where it enters the house.
• Ask your municipality about lead testing and replacement programs.
• Use cold water for drinking and cooking, and flush after water sits.
• Use a filter certified for lead removal as an interim step.
• Replace the full line, city and house side, where possible.
• Keep reducing exposure for 2-3 months after any partial replacement.

References

1. Health Canada. Water Talk: Minimizing exposure to lead from drinking water distribution systems (page details 2016-10-11), Web page, Sources, identifying lead lines, testing, reducing exposure, replacement, partial replacement risk, guideline. Accessed 2026-11-04.

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