THE INCOMING HOSEPIPE bans announced yesterday by Uisce Éireann have brought the huge amount of water used to cool data centres back into the spotlight.

The ongoing spell of hot weather is leading to water shortages and Uisce Éireann said it was now asking people to conserve water for essential use only and restrict the use of hoses.

This has sparked angry reactions online, with politicians and members of the public complaining that the data centre industry has not been put under any restrictions while households and other businesses are.

“We need to know how much of the water consumed in Dublin is consumed by data centres,” People Before Profit TD Paul Murphy said in a post on social media reacting to the announcement of the six-week ban, which will come into effect in Dublin and five other counties from midnight this Thursday.

“We need to know what this consumption increases to during periods of hot weather. We need to know how this affects the water available to meet demand from households,” Murphy said.

He said it was “completely unacceptable that Uisce Éireann and the government can’t or won’t answer these questions when they’ve known for many years that this crisis was approaching”.

Why do data centres need water?

As of June 2025, Ireland was home to 89 data centres, which produce a significant amount of heat.

While much of the public opposition to the proliferation of these facilities has focused on the massive amounts of energy they use, less attention has been paid to the water that is needed to keep many of them cool.

It is not only politicians on the left that have drawn attention to the water used by data centres. One of the most prominent Irish figures who sounded the alarm was former finance minister Paschal Donohoe, not long after leaving the government for a job at the World Bank.  

In most cases, the water used in data centres must be clean so as not to damage the machinery inside. If there is sediment in the water, it can disrupt the flow and erode components, meaning that drinking water is used.

In many data centres, cooling towers are used to keep the temperature down and many of these towers expel heat when this water evaporates. This means that salt water cannot be used because it would leave salt behind when the water turns to vapour. 

Some data centres use air cooling systems, but when temperatures rise above 25 degrees, water must be used because airflow alone doesn’t bring down the temperature enough.

How much water do data centres use in Ireland?

The short answer is we don’t know. 

The Journal Investigates reported in April that the tech industry successfully lobbied the European Union to change legislation to hide the environmental impacts of data centres from the public.

Not all the data centres in Ireland use water from the mains, though. In 2021, 24 of Ireland’s 82 operational data centres were connected to the public water supply.

The Water Forum, Ireland’s statutory body that advises the government on water policy, has said it may be a case that some of those 82 data centres “are small and fit under a different category of customers, or that single water connections may supply water to a number of data centres located on the same site”.

It may also be a case that some data centres in Ireland have their own private water abstractions, the Water Forum said.

A government statement on the role of data centres, published in 2022, said that “Uisce Éireann supplies approximately 608,000 megalitres of water annually, of which 0.13% (c.810 megalitres) is consumed across all known data centres” (a megalitre is one million litres, so in 2022 data centres used roughly 810 million litres of water). 

However, a 2024 report by The Water Forum said that comparing overall supply with data centre consumption is not useful because 38% of the country’s supply is lost through leakage.

Furthermore, the Water Forum report noted that 93% of Ireland’s data centres are located in the Greater Dublin Area (which includes Meath).

“While this value indicates data centres are a low water user, a comparison of water consumed by data centres to a value of water supplied nationally, is not fully transparent on the pressure this industry may have regionally,” the report said, which recommended a regional comparison instead.

The report also noted that the Dublin area has a chronic capacity deficit. An Uisce Éireann plan to divert water from the River Shannon to address that deficit was recently delayed by a year. 

But it’s not just a problem for Dublin, the report said, adding that “some of the existing water abstractions in the Eastern and Midlands region are potentially unsustainable in the medium term; specifically, during drought periods”.

Ultimately, it’s not really known how much data centres are contributing to water shortages in Ireland – though amid an ongoing heat wave where consumers are being asked to conserve water, one can see why people might be eager to find out.