text: Information from the British Drinking Water Inspectorate shows that drinking water in England is generally considered to be very hard, with most areas of England, particularly east of a line between the Severn and Tees estuaries, exhibiting above 200 ppm for the calcium carbonate equivalent. Water in London, for example, is mostly obtained from the River Thames and River Lea both of which derive a significant proportion of their dry weather flow from springs in limestone and chalk aquifers. Wales, Devon, Cornwall and parts of northwest England are softer water areas and range from 0 to 200 ppm. In the brewing industry in England and Wales, water is often deliberately hardened with gypsum in the process of Burtonisation.
  Generally, water is mostly hard in urban areas of England where soft water sources are unavailable. Several cities built water supply sources in the 18th century as the industrial revolution and urban population burgeoned. Manchester was a notable such city in North West England and its wealthy corporation built several reservoirs at Thirlmere and Haweswater in the Lake District to the north. There is no exposure to limestone or chalk in their headwaters and consequently the water in Manchester is rated as very soft. Similarly, tap water in Birmingham is also soft as it is sourced from the Elan Valley Reservoirs in Wales, even though groundwater in the area is hard.