The Drinking Water Inspectorate (DWI) has published its Annual Report for 2024, confirming that the quality of tap water in Northern Ireland remains at a consistently high standard.

According to the report, Northern Ireland Water (NI Water) achieved an overall compliance rate of 99.88% for the public mains supply. This figure is based on a rigorous monitoring programme involving over 100,000 tests conducted at water treatment works, service reservoirs, and consumer taps throughout the year.

Performance Breakdown:

• Public Mains Supply: Achieved 99.88% compliance across more than 100,000 tests.

• Private Water Supplies: The 176 registered private supplies—serving locations such as hospitals, universities, and food manufacturers—showed a slightly lower compliance rate of 99.12% across nearly 13,000 tests.

• Independent Oversight: The DWI, a unit within the Northern Ireland Environment Agency (NIEA), provides independent assurance that these supplies meet more than 50 legal safety standards for bacteria, chemicals, and metals. While overall safety remains high, the report notes significant environmental pressures on raw water sources. Lough Neagh, which provides approximately 40% of Northern Ireland's drinking water, continues to suffer from the impact of blue-green algae (cyanobacteria).

Minister for Agriculture, Environment and Rural Affairs (DAERA), Andrew Muir, welcomed the high compliance but cautioned: "Lough Neagh... is suffering significant water quality impacts. A collaborative, science-led, sustained effort is required to reverse this crisis and safeguard this valuable drinking water source."

In September 2024, two "serious events" were recorded involving the Castor Bay and Moyola Water Treatment Works. While water treatment processes successfully ensured the safety of the water, these events impacted the "acceptability" of the supply (such as taste or appearance) for consumers in those areas.

The DWI emphasised that maintaining these high standards requires continued investment. Work is ongoing through the PC21 process (now extended to 2027) to prioritise funding for water quality and to manage long-term risks within the supply system.