Droitwich Water Hardness & Quality Report (2026)

Droitwich Spa, the Worcestershire spa town famous since Roman times for its underground salt springs — one of the most buoyant natural brines in the world — is supplied by Severn Trent Water from a blend of soft upland water from the Elan Valley Aqueduct (mid-Wales, treated at Frankley) and local groundwater from the Triassic Sherwood Sandstone of the Worcestershire basin. The domestic water supply is entirely separate from the saturated salt brine of the spa springs (the Triassic Keuper Salt beds that made Droitwich famous) but the geology is related. The TDS of 520.9 mg/L for a hardness of 192.5 mg/L (ratio 2.70) reveals a moderate mineral enrichment from the Triassic evaporite sequence — Keuper Marl gypsum and anhydrite interbeds in the sub-surface contribute calcium sulphate to the groundwater blend, elevating TDS above what Elan Valley surface water alone would produce. The irony that Droitwich's fame rests on underground salt while its tap water is modestly mineralised by the same Triassic formation is a distinctive feature of this spa town's water chemistry.

The Triassic Keuper Salt (Halite) beds that produced Droitwich's brine springs underlie the town at 100–200 m depth. At shallower depths, the Keuper Marl and Sherwood Sandstone carry groundwater enriched with calcium sulphate from gypsum dissolution. Severn Trent blends this harder, mildly evaporite-enriched groundwater with the soft Elan Valley supply to produce the 192.5 mg/L hardness of the Droitwich distribution zone — a moderately hard, mildly mineralised supply unlike the extreme concentrated brine of the spa.

At 192.5 mg/L Droitwich's water is moderately hard and limescale is a regular household concern. Kettles benefit from monthly descaling with a citric acid tablet. Shower screens develop a calcium film requiring regular white vinegar treatment. Washing-up liquid lathers adequately. Combi-boilers benefit from inline scale inhibitor protection. Droitwich's elegant spa heritage — Venetian-style brine baths, Georgian architecture and the spirit of St Richard of Droitwich — is underpinned by the most extraordinary underground geology in the Midlands; its domestic tap water, while moderately hard, is a very different and far more benign product of the same Triassic salt basin.