Paisley Water Hardness & Quality Report (2026)

Paisley, in Renfrewshire to the west of Glasgow, is supplied by Scottish Water via the Loch Katrine aqueduct system and the local Renfrewshire reservoir network. The Glasgow and west-central Scotland supply originates primarily from Loch Katrine in the Trossachs — an upland loch draining the Loch Lomond and The Trossachs National Park through granite and Dalradian metamorphic catchment terrain — conveyed through the Victorian Loch Katrine Aqueduct to the Glasgow conurbation. Paisley is also served by the local Renfrewshire Hills reservoir system, with impounding reservoirs in the Gleniffer Braes and Clyde Muirshiel Regional Park uplands feeding the Renfrew network. These upland catchments drain over Carboniferous basalt lava and Old Red Sandstone — relatively insoluble rocks that yield soft, lightly mineralised water.

Paisley's soft water — 60.5 mg/L (4.2°Clark) — reflects the igneous and metamorphic upland geology of the west-central Scotland catchments. Loch Katrine drains a catchment of Dalradian mica-schist and quartzite and Caledonian granite in the Southern Highlands — almost entirely insoluble rocks. The local Renfrewshire Hills are formed from Carboniferous basalt lavas — the remnants of ancient volcanic activity in the Midland Valley of Scotland — which are only slightly more soluble, adding a modest mineral increment. The Drinking Water Quality Regulator for Scotland classifies this supply as soft.

Limescale is minor in Paisley. At 60.5 mg/L, limescale builds slowly and kettles need descaling every two to three months at most. Combi-boiler heat exchangers accumulate only minimal deposits and annual servicing is a sensible precaution rather than a limescale necessity. Showerheads and taps remain largely clear. Washing-up liquid lathers very well with the soft Loch Katrine and Renfrewshire supply. Limescale is rarely a serious concern in west-central Scotland.