St Austell Water Hardness & Quality Report (2026)

South West Water supplies St Austell and much of Cornwall, Devon, and Dorset in South West England. The utility sources water mainly from moorland reservoirs such as Colliford Lake, Roadford Reservoir, and Wistman's Reservoir, alongside upland rivers like the River Tamar and River Fowey. Treatment occurs at plants including the St Austell Water Treatment Works and Crownhill Works near Plymouth. The service area covers approximately 10,600 square kilometers with a population of over 4 million, delivering treated surface water through an extensive network of reservoirs and rivers typical of the region's wet climate.

The watersheds feeding St Austell are the upland catchments of Bodmin Moor and the Lizard Peninsula, characterized by granite intrusions and slate bedrock from Devonian and Carboniferous periods. These impermeable rock formations limit mineral dissolution, producing generally soft water with low dissolved solids. Unlike groundwater from limestone aquifers elsewhere, the surface waters here flow over moorland peats and granite, resulting in very soft, peaty-stained supplies that require minimal mineral removal during treatment. This geology shapes a low-mineralised character, with occasional discoloration from organic moorland runoff.

As a soft water area, St Austell experiences minimal limescale buildup, sparing kettles, irons, and washing machines from common hard water scaling issues. Appliances last longer without descaling, though soft water can feel 'slippery' and may increase corrosion risk in older pipework. No water softener is needed or recommended; instead, focus on occasional boiler flushes if corrosion occurs and use rinse aids in dishwashers for spotting. Energy bills stay lower due to lack of scale in heating elements. South West Water maintains high compliance with UK standards, typically achieving pH 7.0-8.0 and low metals like lead (<10 µg/L) and copper. No notable PFAS exceedances reported in recent DWI data; moorland organics are managed via coagulation and filtration. Treatment involves clarification, ozonation, chloramination, and UV disinfection at plants serving St Austell. Occasional taste/odor issues from peaty sources are addressed seasonally, with full annual quality reports available via postcode lookup on the utility site.