Penicuik Water Hardness & Quality Report (2026)

Scottish Water supplies Penicuik, a former papermaking town on the North Esk in Midlothian at the foot of the Pentland Hills, from Loganlea Reservoir and Glencorse Reservoir impounded on streams draining the Pentland Hills, treated at Glencorse Water Treatment Works before distribution across the Midlothian supply zone. At 53.5 mg/L (3.8°Clark), Penicuik's water is soft, reflecting the upland Pentland Hills reservoir catchments draining ancient metamorphic and volcanic rocks with minimal calcium carbonate content.

The Pentland Hills are composed of Lower Palaeozoic volcanic lavas and tuffs — andesite and basalt sequences from ancient Silurian and Ordovician volcanic episodes — together with ancient greywacke sandstone and mudstone formations, all chemically inert with negligible soluble calcium carbonate. Rainfall draining these inert upland rocks produces naturally soft, slightly acidic water that percolates directly to the reservoirs with minimal mineral acquisition. The resulting supply at 53.5 mg/L with TDS of 109.4 mg/L is characteristically soft, typical of Scottish Water reservoirs on the volcanic hills surrounding Edinburgh.

At 53.5 mg/L, Penicuik's soft water is comfortable for domestic use with very modest limescale demands. Descaling the kettle every two to three months is typically all that is needed. The combi-boiler benefits from a basic scale inhibitor as a precaution against corrosion. Washing-up liquid lathers generously with minimal product. Taps and shower heads remain largely free of limescale deposits with only occasional maintenance. Residents with older copper or lead pipework should briefly flush taps before drawing drinking water, as soft Pentland Hills water can be mildly corrosive to aged metallic plumbing, and a corrosion inhibitor in the central heating circuit is advisable.