Frome Water Hardness & Quality Report (2026)

Frome, the east Somerset market town on the River Frome in the limestone and oolite country at the Mendip–Wiltshire border, is served by Wessex Water. Supply for east Somerset draws primarily on groundwater from the Mendip Hills Carboniferous Limestone Aquifer — the major karst aquifer extending from the Cheddar Gorge and Wookey Hole area east to the Somerset–Wiltshire chalk border — and from the Jurassic Great Oolite limestone that underlies the gently rolling farmland immediately south and east of Frome. Wessex Water treats groundwater at Shepton Mallet and Brewham Water Treatment Works before distribution through the east Somerset network. The very high TDS of 730.5 mg/L at 252 mg/L hardness reflects the long-residence carbonate groundwater character of both the Carboniferous limestone and Jurassic oolite aquifers, enriched with calcium bicarbonate and sulphate from the thick Somerset limestone sequences.

The Carboniferous Limestone (Dinantian) of the Mendip Hills is a thick karst aquifer in which groundwater travels along cave passages and dissolution conduits for kilometres before emerging at springs such as Wookey Hole and the Cheddar springs. This prolonged residence in reactive carbonate rock allows calcium bicarbonate to reach near-saturation at 240–260 mg/L. The overlying and adjacent Great Oolite (Bath Stone) of the Somerset–Wiltshire plain adds further calcium carbonate enrichment. Together these two Carboniferous and Jurassic carbonate systems produce Frome's consistently very hard supply at 252 mg/L — among the hardest in south-west England.

At 252 mg/L Frome's water is very hard and limescale is a persistent and serious domestic problem. Kettle elements require fortnightly descaling with a concentrated citric acid solution to prevent heavy scaling. Shower screens accumulate a white calcium crust without weekly chemical treatment — white vinegar spray applied and wiped regularly is essential. Washing-up liquid produces poor lather without generous amounts. Combi-boilers require inline magnetic scale inhibitors and regular annual servicing to avoid costly scale-related failures. Frome's growing reputation as a creative and artisan town contrasts with the relentless hard Mendip limestone water that challenges every household appliance throughout the town.