Perth Water Hardness & Quality Report (2026)

Perth, the historic city on the River Tay at the Highland boundary, is supplied by Scottish Water from Loch Turret reservoir in the Ochil Hills and the River Tay catchment supply network. Loch Turret sits in the hills south-west of Crieff, collecting water from Grampian metamorphic catchments of the south Highlands — Dalradian schist and Grampian Group metasedimentary rocks that contribute essentially no dissolved calcium to runoff. The River Tay rises on Rannoch Moor and drains the Grampian Mountains and Highland glens — vast areas of ancient Dalradian and Moine metamorphic rocks. Scottish Water treats and distributes the Tay/Turret supply to Perth and the Tayside area. The TDS of only 40 mg/L reflects the exceptional mineral purity of the Perthshire Highland supply.

Perth's exceptionally soft water — 20 mg/L (1.4°Clark) — reflects the Dalradian and Grampian metamorphic rock catchments of the Perthshire Highlands. These ancient metamorphic basement rocks are virtually calcium-free, producing upland loch water of remarkable purity. The Drinking Water Quality Regulator for Scotland classifies this supply as very soft.

Limescale is essentially absent in Perth homes. At 20 mg/L, limescale will not form under any normal domestic circumstances — kettles need descaling very occasionally and taps, showerheads, and shower screens remain completely clear. Washing-up liquid lathers exceptionally well. The very low hardness and slightly acidic pH of Perth's supply means Scottish Water carefully manages pH to prevent any potential copper pipe leaching in older properties. Perth households in Victorian or Edwardian properties with original copper plumbing should check with Scottish Water about pH management and consider a calcite filter if concerned about trace copper in drinking water.