From today householders will be banned from using hosepipes to water the grass or wash their car.
Irish Water says it's introducing the measure, which will be in place for the next six weeks, in the wake of the driest May since 1850.
The utility says 77 of the its drinking water schemes are in drought or at risk of drought.
It also says progress is being made to reduce the number of leaking pipes after criticism that may be contributing to the shortage.
Tom Cuddy from Irish Water says among the ways a previous ban was enforced was neighbours contacting them.
"We had a hosepipe ban in 2018, and we received complaints from members of the public.
"We looked at our own meter data, and also our own staff - we have between our own staff, the local authorities and our contractors, we probably have about 4,000 staff down on the ground, so we got a lot of information from those sources."
