As you know, in Canada Health Canada establishes the maximum acceptable concentrations through the guidelines for Canadian drinking water quality. Then they are adopted or not adopted by each province as the province sees fit.
One difficulty in Canada is that the level of adherence to the guidelines for Canadian drinking water quality varies from province to province. Some provinces, like Nova Scotia, fully adopt the guidelines for Canadian drinking water quality. Other provinces create their own but similar guidelines. Some provinces just adopt the ones they think are important to their province, and lead would be...I wouldn't say discretionary, but something for which the guidelines would be followed by some provinces but not by others.
Then all municipalities are regulated differently within their province. Some utilities are larger and have more resources to deal with the problem; others are smaller and don't have the resources.