Risca Water Hardness & Quality Report (2026)

Dŵr Cymru Welsh Water supplies Risca, a town in the Sirhowy Valley of Caerphilly county borough, from upland reservoirs set within the South Wales coalfield valleys. The primary sources serving the Caerphilly and lower valley area include upland impoundments in the Brecon Beacons catchment and local Sirhowy and Ebbw valley reservoirs, treated at regional works before distribution. At 63.5 mg/L (4.5°Clark), Risca's water is soft, reflecting the dominance of acid moorland and coal measure catchments that produce naturally low-mineralisation surface water throughout the South Wales valleys.

The South Wales Coalfield geology of the Sirhowy Valley consists of Carboniferous Coal Measures — interbedded sandstones, mudstones, and coal seams containing minimal soluble calcium carbonate. Upland catchments in this region are dominated by acid grassland, rush pasture, and blanket bog overlying thin, base-poor soils. Rainfall draining these formations dissolves very little calcium carbonate, producing soft to very soft runoff. The modest hardness recorded in Risca's supply reflects minor dissolved calcium from glacial till deposits and pH adjustment chemicals added during treatment to stabilise the water.

At 63.5 mg/L, Risca's soft water is very gentle on household appliances and fittings. Limescale formation is slow; descaling the kettle every two to three months is generally sufficient to keep it performing well. The combi-boiler is unlikely to develop significant limescale deposits at this hardness level, though a scale inhibitor remains good practice. Washing-up liquid lathers very freely in this soft water at everyday quantities. Taps and shower heads remain limescale-free for extended periods with minimal maintenance. Residents should note that soft water can be slightly more corrosive to old lead or copper pipework, so flushing taps briefly before drawing drinking water is advisable if the property has older plumbing.