July 21st, 2022

Ontario’s surface and groundwater generally does not contain lead. If lead does occur naturally, the concentrations are typically extremely low and below the drinking water standard for lead. Where there are concentrations of lead in drinking water above the standard, the likely cause is from the lead pipes servicing the premises, lead solder used in the plumbing or fixtures containing high percentages of lead.

Lead pipe service connections have been used to deliver water from distribution pipes since the late 1800s. Older buildings (generally those built before the mid-1950s) are more likely to have lead connections. By 1990, the amount of lead in solder that could be used in drinking water plumbing was substantially reduced.

The amount of lead leaching into drinking water from these components depends largely on the chemical characteristics of the water. In certain circumstances, extended contact between standing water and the components can cause the lead to be released from the pipes. When the tap is turned on, water that has been standing in the pipes may have accumulated lead levels higher than Ontario’s standard for lead.