Irish Water has announced a nationwide hosepipe ban will come into effect from tomorrow for a six-week period.
It is blaming recent dry conditions and an increase in domestic water usage during the Covid-19 lockdown.
Irish Water says increased domestic demand during the Covid-19 lockdown has come at the same time as warm weather, which has brought drought conditions to parts of the country.
The company said that 27 of its drinking water schemes are in drought and 50 are at risk - out of a total of 900 water schemes nationally.
Supplies are also facing greater demand as businesses being to reopen after the lockdown.
The Water Conservation Order bans garden hosepipes and other non-essential use such as filling paddling pools and washing cars. People are being advised to re-use household water for the garden and to take shorter showers.
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Managing Director of Irish Water Niall Gleeson has appealed to the public not to buy or use large paddling pools, not to use hosepipes to water their gardens, and not to wash their cars with hosepipes.
He told RTÉ's Morning Ireland that conservation was needed to keep water for hygiene purposes and to allow businesses to return.
The ban will remain in place until Tuesday 21 July and will be reviewed, depending on weather conditions, he said.
Mr Gleeson said that spring has been one of the driest on record with predictions of dry conditions set to continue.
He said there has been a rise in domestic usage of water by people who have been in lockdown at home and now as businesses are starting to return supplies are being further stressed.
Mr Gleeson said over the June Bank Holiday weekend the increase in water usage was equivalent to the demand of an additional 200,000 people in the Greater Dublin region and this dropped the following week showing it was not essential use.
He said 38% leakage continues in the system but Irish Water continues to make 1,500 repairs to burst pipes each month and are playing "catch up" on leaks all the time.
He said even if all the leaks were fixed, more supply is needed as well as conservation.
He urged people not to use water for "frivolous" or non-essential reasons over the next six weeks as the availability of supply is very low.
Met Éireann said May was the driest since 1850, temperatures were above average in nearly all areas and rainfall totals in every county were below normal for the time of year.