Edinburgh Water Hardness & Quality Report (2026)

Edinburgh's water supply is managed by Scottish Water, with its primary sources in the upland reservoirs of the Scottish Borders. Talla Reservoir in Peeblesshire, completed in 1905, and Megget Reservoir, opened in 1983 as Scotland's largest dam by volume, form the backbone of the capital's supply, augmented by Fruid Reservoir. Water is conveyed to the city by gravity and treated at Glencorse Water Treatment Works on the southern outskirts of Edinburgh, a facility originally constructed in the 1870s and progressively modernised since. The system represents one of Scotland's most significant pieces of public infrastructure, supplying the capital and much of the Lothians.

Edinburgh's water hardness of 25 mg/L (1.8°Clark) reflects the geology of the Borders upland catchments. The Talla and Megget catchments are underlain by Silurian greywacke, mudstone, and shale — ancient impervious marine sedimentary rocks formed over 420 million years ago that weather very slowly, releasing minimal calcium or magnesium into draining water. Despite Edinburgh's own geology featuring dramatic volcanic features such as Arthur's Seat and Castle Rock, the city's tap water comes entirely from the upland Border reservoirs, resulting in a very soft supply classified as soft by the Drinking Water Quality Regulator for Scotland.

Limescale accumulation in Edinburgh homes is minimal. At just 25 mg/L, limescale in kettles develops only slowly — most Edinburgh households find descaling is needed only once or twice per year. Combi-boilers in Edinburgh properties are largely unaffected by limescale deposits inside heat exchangers, maintaining efficient operation without specialist water softening. Taps, showerheads, and bathroom tiles remain largely free of limescale build-up with normal cleaning. Washing-up liquid lathers easily with minimal product waste. As with much of Scotland, the primary consideration is that Edinburgh's soft, slightly acidic water can be corrosive to older copper and lead pipework — Scottish Water maintains pH adjustment at treatment, but older Edinburgh tenements should ensure their plumbing has been fully updated.