Diss Water Hardness & Quality Report (2026)

Anglian Water supplies Diss, the south Norfolk market town at the Norfolk–Suffolk border — a pleasant market town with a large central Mere (a natural lake of glacial origin), an independent high street and Friday market that has served the Waveney Valley since medieval times, and a position on the Great Eastern Mainline making it a favoured base for Norwich and London commuters — from the Norfolk–Suffolk Chalk (Cretaceous) aquifer boreholes in the south Norfolk supply zone, treated at Whitlingham Water Treatment Works near Norwich. At 299.5 mg/L (21.0°Clark) and a TDS of 831.9 mg/L, Diss's water is extremely hard — consistent with the deep productive Cretaceous Chalk and Crag aquifer system of south Norfolk and north Suffolk that delivers persistently very hard groundwater.

Diss lies in the south Norfolk chalk belt at the Waveney Valley where Anglian Water draws from deep Upper Chalk (Cretaceous) boreholes. The chalk delivers concentrated calcium carbonate, enriched by sulphate from the Red Crag and Norwich Crag (Pliocene marine sediments) overlying the chalk, producing 299.5 mg/L with TDS 831.9 mg/L — extremely hard water with an elevated TDS/hardness ratio (2.78) characteristic of the south Norfolk and north Suffolk chalk and Crag supply zone.

At 299.5 mg/L, limescale is a severe household problem in Diss. Kettles should be descaled every week to ten days. The combi-boiler requires a fitted scale inhibitor and annual professional servicing as a minimum. Washing-up liquid requires very generous quantities. Taps and shower heads develop heavy chalk deposits within days; frequent descaling with white vinegar or a proprietary product is necessary. A whole-house water softener is strongly recommended for Diss households — at 299.5 mg/L, the south Norfolk chalk supply is among the hardest in England, and protecting appliances from limescale is a practical investment rather than an optional comfort.