Bushey Water Hardness & Quality Report (2026)

Bushey, the south-west Hertfordshire town adjacent to Watford and straddling the River Colne valley, is served by Affinity Water. Supply to the south-west Hertfordshire and Watford corridor draws on deep boreholes sunk into the Chiltern Chalk Aquifer — the thick Cretaceous White Chalk that underlies the whole of south Hertfordshire and dips south-east toward London. Affinity Water's Central Region boreholes at Bushey, Croxley Green and the Watford area abstract chalk groundwater that has resided in the aquifer for decades. Water is treated at Bushey Water Treatment Works before distribution through the south-west Hertfordshire network. The very high TDS of 869.1 mg/L reflects a supply highly concentrated in dissolved calcium bicarbonate from long-residence confined chalk groundwater, with additional sulphate and sodium from the Reading Formation directly above the chalk in this zone.

The Upper Cretaceous Chalk beneath south-west Hertfordshire is overlain by London Clay and Reading Formation deposits, which confine the chalk aquifer beneath Watford and Bushey. Groundwater within this confined chalk undergoes no dilution from younger infiltration, allowing calcium bicarbonate to accumulate over time to concentrations approaching 300 mg/L before abstraction. The TDS substantially exceeding 800 mg/L points to the additional ion contribution from the Reading Formation clays and sands through which water percolates before reaching the chalk boreholes. The hardness here is noticeably elevated compared with less-confined parts of the Chiltern chalk to the north.

At 300 mg/L Bushey's water is very hard — at the threshold between very hard and extremely hard — and limescale management is intensive. Kettle elements need fortnightly descaling with a citric acid solution to stay functional. Shower screens and glass shower doors require weekly limescale treatment and daily squeegeeing to maintain visibility. Combi-boilers face high scaling risk and must have magnetic scale inhibitors installed and be serviced annually. Washing-up liquid must be used in large quantities for satisfactory lather. Many Bushey households invest in whole-house water softeners; the south Hertfordshire hard-water corridor is one of the most challenging domestic water supply areas in England.