Nuneaton Water Hardness & Quality Report (2026)

Nuneaton, the largest town in Warwickshire in north Warwickshire, is supplied by Severn Trent Water from the combined Welsh upland aqueduct and local groundwater network. The primary supply originates from the Elan Valley Reservoir system in mid-Wales, but Nuneaton's north-east Warwickshire position means its supply incorporates a substantial proportion of groundwater from the Triassic Mercia Mudstone (Keuper Marl) and Sherwood Sandstone aquifers beneath north Warwickshire and east Staffordshire. The Triassic geology of the north Warwickshire plain — red mudstones and sandstones deposited in desert conditions approximately 230–240 million years ago — yields groundwater with significant dissolved calcium and sulphate content from mudstone and evaporite mineral dissolution. This local groundwater raises Nuneaton's hardness well above the soft Elan Valley baseline.

Nuneaton's hardness of 233.5 mg/L (16.4°Clark) — far above Birmingham's 60–80 mg/L — reflects the strong Triassic Mercia Mudstone groundwater influence in the north Warwickshire distribution zone. The Mercia Mudstone and associated Triassic evaporite mineral beds beneath north Warwickshire yield groundwater with elevated calcium, sulphate, and magnesium — a mineralised groundwater signature distinct from the soft Welsh upland supply. The Severn Trent distribution blend serving Nuneaton receives a high proportion of this local Triassic groundwater, producing a hard supply. The Drinking Water Inspectorate (DWI) classifies this supply as hard.

Limescale is a persistent household challenge in Nuneaton. At 233.5 mg/L, limescale forms in kettles within two to three weeks and monthly to fortnightly descaling is advisable. Combi-boiler heat exchangers accumulate limescale deposits steadily — annual boiler servicing with a limescale check is essential, and fitting an in-line scale inhibitor is strongly recommended. Showerheads, taps, and shower screens develop regular heavy deposits. Washing-up liquid lathers noticeably poorly. Using Calgon monthly in the washing machine and maintaining a regular descaling routine is important for Nuneaton households.