Drinking water in Scotland in 2025: 99.91% compliance in 296,935 tests; at consumers’ taps the fall in compliance was almost entirely due to 45 chlorate exceedances
On 27 August 2026 the Drinking Water Quality Regulator for Scotland (DWQR) published its report for 2025 on the public water supply provided by Scottish Water. Of 296,935 regulatory tests, 255 exceeded the standards — compliance was 99.91%, compared with 99.94% in 2024, when there were 205 exceedances.
- Scottish Water takes and analyses its own samples — as water leaves treatment works, in service reservoirs and at randomly selected consumers’ taps. Sampling and analysis are independently accredited, and DWQR independently assesses the monitoring programme and its results.
- 137,947 tests were carried out at consumers’ taps and 99.88% complied (168 exceedances). The decline was almost entirely due to 45 chlorate exceedances in 18 supply zones (out of 3,542 chlorate tests; prescribed value 0.25 mg/l) — which, according to DWQR, points to the need for better storage and management of sodium hypochlorite at treatment works.
- E. coli was not detected in any of the 25,585 tests of water leaving treatment works; coliform bacteria failed the standard in 20 tests at 18 works. In service reservoirs 65 of 96,854 tests failed, and DWQR notes no significant improvement in their performance over the past decade.
- Consumers made 17,558 contacts about water quality (5% more than 16,779 in 2024), mostly about discolouration. Scottish Water notified the regulator of 1,086 events (866 a year earlier), and DWQR investigated 36 incidents — two more than in 2024.
Source: DWQR — Drinking Water Quality in Scotland 2025: Public Supplies Annual Report (27.08.2026)