A laboratory lead‐pipe rig has been used to support Anglian Water's successful orthophosphate dosing programme to reduce plumbosolvency. The hard waters in the region generally fall into low or high plumbosolvency categories according to the types of crystalline deposit formed. To improve the cost‐effectiveness of plumbosolvency control, the effects of temperature, phosphate doses, blending and alternation of these waters were investigated. Initial phosphate concentrations must be above 0.6 mg P/l (as phosphorus) to establish plumbosolvency control. Subsequently, phosphate doses may be reduced, provided that dosing is continuous and sufficient phosphate reaches the extremities of the distribution system. When high and low plumbosolvency waters are blended before distribution, both (or the mixture) must be phosphate dosed. However, where waters alternate in distribution, laboratory studies have shown that low plumbosolvency deposits are more stable, resulting in low lead concentrations. The high plumbsolvency of some hard waters may be due to the presence of low concentrations of humic substances.

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Diffuse pollution by pesticides, particularly herbicides, has been recognized in the UK for several years. Atrazine, Simazine, Mecoprop, Dimethoate and, more recently, Isoproturon and Chlortoluron have been found frequently in surface waters at concentrations up to 0.5 &1, with a maximum of 11.5 pg/l. Pesticides are detected less frequently in groundwaters, at concentrations generally lower than 0.1 pg/l. Atrazine is found most frequently. Concentrations in untreated surface and groundwaters have generally been below the maxima recommended for drinking water by the Department of the Environment (DOE). Concentrations in treated drinking water have not exceeded the DOE recommended maximum concentrations, but measures are being taken to reduce concentrations to below 0.1 pgl.