Latest figures show 99.88% compliance for NI drinking water

Northern Ireland’s drinking water remains among the safest in these islands — but pressure is building beneath the surface.

The Drinking Water Inspectorate (DWI) has this week published its Annual Report for 2024, confirming that drinking water quality across Northern Ireland continues to meet an exceptionally high standard.

The figures are strong: 99.88% overall compliance for the public mains supply, based on more than 100,000 tests carried out during the year.

The results cover samples taken from water treatment works, service reservoirs and consumers’ taps, under a stringent monitoring programme undertaken by Northern Ireland Water Limited (NI Water) to ensure compliance with drinking water regulations.

Welcoming the report, Minister for the Department of Agriculture, Environment and Rural Affairs (DAERA), Andrew Muir said:

“I am pleased to endorse the Drinking Water Inspectorate’s annual report on Drinking Water Quality in Northern Ireland. The quality of our drinking water is vital for public health, the hospitality sector, farming and the economy.

“The Drinking Water Inspectorate has an important role to play in providing the Northern Ireland public with independent assurance that their water supply is safe and clean.

“Lough Neagh, which provides 40% of our drinking water in Northern Ireland, 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.”

Lough Neagh pressure point

While compliance remains high, the report highlights ongoing risks linked to blue-green algae (cyanobacteria) blooms in raw water sources — particularly Lough Neagh, which supplies around 40% of Northern Ireland’s drinking water.

Although treatment processes are designed to manage these risks and protect public health, two serious events occurred in September 2024 concerning the acceptability of water supplied from Castor Bay and Moyola Water Treatment Works. Both facilities draw water from Lough Neagh.

The Inspectorate emphasised the importance of managing risks across the water supply system and underlined the need for an appropriately funded investment programme.

Throughout 2024, DWI continued working with stakeholders to prioritise investment in drinking water quality through the PC21 process, which has been extended to include 2027.

Private water supplies also monitored

While the vast majority of homes and businesses rely on the public mains network, a small percentage of water is supplied from private sources. In 2024, there were 176 registered private water supplies across Northern Ireland, including eight newly registered sites.

Many of these serve public buildings such as hospitals and healthcare premises, universities, and businesses including food and drink manufacturers, hotels and restaurants.

Almost 13,000 tests were carried out on private supplies during the year. The overall compliance rate stood at 99.12% — slightly lower than the public supply figure, but still high.

Independent oversight

The Drinking Water Inspectorate operates as a business unit within the Northern Ireland Environment Agency (NIEA), part of DAERA, and has an independent responsibility to assess and regulate drinking water quality across both public and private supplies.

NI Water remains solely responsible for the supply and distribution of public drinking water.

The full report is available on the Department’s website.

With compliance rates remaining strong but environmental pressures intensifying — particularly around Lough Neagh — the message from 2024 is clear: Northern Ireland’s water remains safe, but safeguarding it will demand sustained focus, investment and science-led action in the years ahead.