Plymouth Water Hardness & Quality Report (2026)

Plymouth's water supply is managed by South West Water, with its primary source being Burrator Reservoir in Dartmoor National Park — a Victorian impoundment on the River Meavy completed in its original form in 1898 and enlarged in 1929, with a capacity of approximately 4.5 billion litres. Burrator is supplemented by Avon Dam and the wider Dartmoor catchment collection system, including smaller reservoirs at Sheepstor and Drakeford. Water is treated at Crownhill Water Treatment Works in Plymouth before distribution to one of the UK's largest naval and maritime cities. Dartmoor National Park's vast upland catchment area provides high-quality, naturally clean source water.

Plymouth's very soft water — 45 mg/L (3.2°Clark) — is a direct consequence of Dartmoor's granite geology. The Dartmoor batholith is a large mass of coarse-grained Variscan granite intruded into the surrounding Devonian sedimentary rocks approximately 300 million years ago. Granite is a highly resistant igneous rock, almost entirely impermeable to chemical weathering by natural drainage. Rainfall on Dartmoor runs off the moorland surface and bogs into the reservoirs with virtually no opportunity to dissolve calcium or magnesium from the underlying rock. The result is one of the softest public water supplies of any major city in England.

Limescale is rarely a practical concern for Plymouth households. At 45 mg/L, limescale accumulates very slowly — kettles may show only a faint film after several months, and descaling once or twice a year is ample. Combi-boilers face negligible limescale stress, with minimal heat exchanger deposits anticipated over many years of operation. Washing-up liquid lathers very generously with little product needed, and taps and showerheads remain largely clear of limescale with regular cleaning. One consideration specific to Plymouth is the combination of soft water and older housing stock in areas near the city centre — soft water's mildly corrosive properties make a brief early morning tap flush worthwhile in any property retaining original lead service pipes.