In England and Wales regulations require audit monitoring for lead through random daytime (RDT) sampling at customers taps, and specify up to 8 samples per year per zone. Because of the historically high lead risk in the north-west of England the regulatory programme has been supplemented by a much larger operational programme. This has provided an opportunity to analyse a large data set of 62,823 samples, collected over the period 2006 to 2010 when plumbosolvency treatment conditions were fairly consistent, and compliance is high. The samples were analysed by inductively coupled plasma mass spectrometry to standards laid down by regulation and UKAS accredited.