At the zonal scale (e.g. a city or town), random daytime (RDT) sampling succeeded in demonstrating both the need for corrective action and the benefits of optimised orthophosphate dosing for plumbosolvency control, despite initial concerns about sampling reproducibility. Stagnation sampling techniques were found to be less successful. Optimised treatment measures to minimise lead in drinking water, comprising orthophosphate at an optimum dose and at an appropriate pH, have succeeded in raising compliance with the future European Union (EU) lead standard of 10 μg/L from 80.4% in 1989–94 to 99.0% in 2010 across England and Wales, with compliance greater than 99.5% in some regions. There may be scope to achieve 99.8% compliance with 10 μg/L by further optimisation coupled to selective lead pipe removal, without widespread lead pipe removal. It is unlikely that optimised corrosion control, that includes the dosing of orthophosphate, will be capable of achieving a standard much lower than 10 μg/L for lead in drinking water. The experience gained in the UK provides an important reference for any other country or region that is considering its options for minimising lead in their drinking water supplies.

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