Irish Water has issued the ban, legally called a water conservation order, for 40,000 people using 30 severely depleted supplies in west Cork, where water levels have dropped to “historic lows”.
It will begin at midnight and run for four weeks, but may be extended if not enough rain falls to replenish supplies before then.
Irish Water is also warning that other parts of the country, particularly in Wexford, Galway, Tipperary and Kerry, need interventions such as tankering and pressure reduction to keep taps running.
Dozens of other supplies, particularly in the midlands, are under close watch as levels drop, with below average rainfall due in the coming weeks.
Non-essential water uses are prohibited under the ban, including using hoses to water lawns and plants, wash private cars or leisure boats, and fill swimming pools or ponds.
Small paddling pools may be filled if it can be done with a hand-held container filled from a normal tap, and ponds with fish may also be replenished, but other water features such as fountains and artificial lakes must not. “Using a hosepipe for one hour is the equivalent of the daily water usage of an average family and this is generally a non-essential use of water,” Margaret Attridge, Irish Water regional manager, explained.
Anyone found flouting the ban may be fined €125.
Irish Water said the conservation order was needed after a long period of dry weather combined with a large increase of demand left west Cork water supplies under “severe stress”.
Areas affected include busy towns such as Clonakilty, Skibbereen and Bantry, along with many smaller, more remote communities such as Goleen, Cape Clear and Dursey Island.
Since November 2021 rainfall in the region has been below average for every month except last June.
Irish Water said six to eight weeks of rainfall were needed to replenish supplies.
Just 6.3mm of rain fell at the weather station in Roches Point over the 10 days up to last Tuesday.
By comparison, the station at Mullingar recorded 18.4mm and Markree Castle in Sligo had 32mm over the same period, which was not particularly wet.
Met Éireann is forecasting mainly dry weather this week and while next week is to be wet all over the country, another dry spell is expected for the following two weeks.
Irish Water said this would increase the pressure on already depleted supplies.
“Water levels at our surface water and ground water sources in the west Cork area have reduced to historic lows,” Ms Attridge said.
She said night-time shut-offs, pressure reduction, public appeals to ease off on usage and tankering water in to boost supplies had all been tried first but the situation had not improved.
“As demand continues to outstrip supply in west Cork and with further dry weather predicted, we have taken the extra step of implementing a water conservation order to safeguard supplies,” she said.
“We will continue to analyse water consumption levels while the water conservation order is in place.
“It is essential that our water supply is protected if we are to avoid restrictions and outages over the coming weeks and months.”
The last hosepipe ban was in 2020 and before that in 2018. Both covered the entire country for periods.