Croxley Green Water Hardness & Quality Report (2026)

Affinity Water supplies Croxley Green, a leafy commuter village in south-west Hertfordshire near Watford and the Grand Union Canal — set on the chalk plateau above the Colne Valley and served by the Metropolitan Line at Croxley Green (now Watford) station — from Chiltern Chalk aquifer boreholes in the Colne Valley chalk zone, treated at Croxley Hall Water Treatment Works near Rickmansworth. At 310.5 mg/L (21.8°Clark) and a TDS of 921.4 mg/L, Croxley Green's water is extremely hard — among the hardest in Hertfordshire — consistent with the deeply confined Chiltern Chalk borehole supply that defines the extreme hardness of the Affinity Water Colne Valley distribution zone.

Croxley Green sits on the Chiltern Chalk plateau where the Upper Chalk (Cretaceous) lies at or near the surface, fully unconfined and freely recharged by Chiltern rainfall. Affinity Water draws on this productive chalk borehole supply at multiple Colne Valley sites, extracting deeply mineralised calcium bicarbonate groundwater with TDS 921.4 mg/L at 310.5 mg/L hardness — a supply characteristic of the very hard Chiltern chalk belt from Amersham through Rickmansworth to Watford. The Croxley Green supply zone consistently ranks among England's hardest, rivalling even the hardest south-east London zones.

At 310.5 mg/L, limescale is an extreme and persistent household problem in Croxley Green. Kettles must be descaled weekly to prevent rapid element failure. The combi-boiler faces very high risk of premature breakdown without a properly fitted, annually replaced scale inhibitor and regular professional servicing. Washing-up liquid barely lathers without very generous quantities of product. Taps, shower heads, and basin fittings develop heavy chalk encrustation within days; a weekly descaling with white vinegar or a proprietary product is essential. A whole-house water softener is very strongly recommended for all Croxley Green households.