Renfrew Water Hardness & Quality Report (2026)

Renfrew, the historic burgh on the south bank of the River Clyde in Renfrewshire west of Paisley — the birthplace of the Scottish House of Stewart — is supplied by Scottish Water from Loch Katrine in the Trossachs, transported via the Katrine–Milngavie Aqueduct to Milngavie Water Treatment Works north of Glasgow before distribution south through Renfrewshire. Loch Katrine drains the Loch Lomond and The Trossachs National Park — a vast catchment of Dalradian metamorphic schist, Ordovician greywacke and Caledonian granite that produces some of the purest, softest freshwater in the United Kingdom. At 22.5 mg/L with TDS of only 39.2 mg/L, Renfrew's water is the softest in this dataset — and among the very softest urban water supplies in England, Scotland or Wales. The Victorian-era Glasgow and Loch Katrine water scheme, completed in 1859 and engineered by J. F. Bateman, remains one of Britain's greatest engineering achievements, still delivering exceptionally soft Highland water daily.

The Dalradian metamorphic schist and Caledonian granite of the Trossachs and Loch Katrine catchment are ancient Precambrian to Cambrian rocks utterly devoid of calcium carbonate. Atlantic rainfall falling on these mountains percolates through thin acid highland soils and drains into Loch Katrine, accumulating virtually no dissolved minerals. With a TDS of only 39.2 mg/L — barely above the mineral content of commercially bottled soft spring water — Renfrew's supply represents the near-minimum mineral content achievable in any public water supply system. This near-distilled-quality water has served Renfrewshire and south-west Glasgow since the Victorian aqueduct first opened.

At 22.5 mg/L Renfrew's water is exceptionally soft — limescale is completely absent as a domestic concern. Kettles may be used for months or years without any descaling. Shower screens remain perfectly clear. Washing-up liquid froths abundantly with the smallest quantity. Combi-boilers and white goods enjoy effectively unlimited lifespans from a scaling perspective. The practical consideration for Renfrew's older housing stock — traditional sandstone tenements and Victorian terraces — is that very soft water can be slightly corrosive to lead-solder joints in old copper plumbing and original lead pipework. Properties with pre-1970s plumbing should consider having lead sections tested and replaced for health reasons.