South West Water Tap Water Quality

South West Water supplies Devon, Cornwall, Dorset & Somerset with drinking water drawn from upland moorland reservoirs on Dartmoor, Exmoor, and Bodmin Moor, with some lowland abstractions in Dorset.

South West Water supplies some of the softest water in England. Dartmoor, Exmoor, and Bodmin Moor are granite upland catchments that produce very low-mineral, naturally acidic water — hardness is typically 20–60 mg/L. The low mineral content means excellent appliance longevity, but the corrosive nature of the water requires careful pH correction treatment to prevent leaching of copper and lead from household plumbing. Colour from peat in the source water is a monitoring parameter at some moorland catchments. Following the 2023 merger with Bournemouth Water, coverage expanded into Dorset, where some zones are harder due to chalk geology.

Typical water profile

With typical hardness of approximately 50 mg/L CaCO₃, water in the South West Water supply area is classified as soft. This means minimal limescale risk and good appliance longevity across the supply area.

Notable: Among the softest water in England. Very low limescale risk. pH correction required to reduce corrosiveness. Some colour in peat-influenced sources. Active PFAS programme under DWI enforcement.

Is South West Water water safe to drink?

Yes. All treated water supplied by South West Water meets the UK Drinking Water Regulations. The Drinking Water Inspectorate (DWI) audits every water company annually — South West Water serves 1.8 million customers across 29 supply zones. Each zone is tested thousands of times per year and results are published in the annual compliance report.

However, water quality varies significantly between zones within the South West Water supply area. Your specific zone may have different hardness, nitrate, or THM levels from your neighbour in a different zone. That's why it's worth checking your exact postcode above.

How to check your South West Water zone

Enter your postcode in the box above to see zone-specific data for your address — including hardness, nitrates, lead, chlorine, fluoride, and THMs — drawn directly from South West Water's most recent annual compliance report.