Irish Water is warning that supplies could be restricted until the autumn.
The hosepipe ban will be extended this week to Laois, Kilkenny, Limerick, Kerry, Galway and Waterford.
It started in the greater Dublin area on Monday to try and counteract falling reservoir levels during the heatwave.
Managing Director of Irish Water, Jerry Grant, doesn't expect things to improve any time soon: "The kind of drought that we're seeing at the moment shows that there are serious deficit in groundwater levels, unless we get torrential rainfall in August that we sometimes do we will see a very slow recovery."
