Portsmouth Water has published its 2025 annual water quality report, and MyTapWater has refreshed all 15 of the company's supply zones with the new figures. Nitrate, hardness, lead, fluoride and the full parameter set now reflect the 2025 sampling year across the Portsmouth Water area.
Portsmouth Water supplies around 300,000 properties across south-east Hampshire and the West Sussex border, drawing almost entirely on chalk groundwater from the South Downs. That chalk source is the defining feature of the area's water, and the 2025 figures confirm it: the supply is consistently hard, with zone hardness ranging from roughly 267 to 315 mg/L as calcium carbonate — firmly in the "hard" band — and the highest readings in the Worlds End and Littleheath zones.
What the 2025 nitrate data shows
Nitrate is the parameter most worth watching in a chalk-groundwater supply, because nitrate from historic agricultural land use migrates slowly into the aquifer over decades. In the 2025 report, zone mean nitrate ranges from about 24.6 mg/L (Worlds End) to 38.4 mg/L (Lovedean), all within the 50 mg/L legal limit. Lovedean carries the highest reading, with a single maximum sample of 49.2 mg/L — close to, but under, the limit — consistent with its position over intensively farmed chalk downland.
Lead and fluoride
Lead readings across all 15 zones are low, with zone means between 0.5 and 1.9 µg/L against the 10 µg/L limit measured at the tap. As always with lead, the figure that matters most for an individual home is whether that property has an older lead supply pipe, rather than the zone average — you can estimate that with our lead pipe risk checker, or read our guide to lead in tap water. Fluoride is naturally low throughout the Portsmouth Water area (zone means around 0.08 to 0.39 mg/L), and the supply is not artificially fluoridated.
How this fits the wider picture
Portsmouth Water is one of the 22 companies and 1,614 supply zones MyTapWater tracks. The 2025 refresh brings the company up to date in our data — its zones previously reflected the 2024 report — so postcode lookups, hardness figures and parameter breakdowns for the Portsmouth area now draw on the latest published year. The previous year's figures are retained in our history record, so the year-on-year change for each zone is preserved.
Portsmouth Water is also among the 14 companies with an active DWI PFAS improvement programme — part of the national monitoring and treatment effort, with target completion dates set by the regulator, rather than a reflection of current supply. Enter your postcode below for the full 2025 breakdown for your zone.
Source: Portsmouth Water 2025 water quality summary reports (per supply zone) and 2025 hardness values, published July 2026.