Better known as a hosepipe ban, the notice is in effect from 8am this Friday, July 6 until midnight on Tuesday, July 31 as a drought continues across the country.
A hosepipe ban is already in place across Dublin and its surrounding areas, after being brought in on Monday.
"Our top tips are to limit time spent in the shower to no more than four minutes, use a watering can to water garden plants, and to hold off on cleaning the vehicle but if you have to wash it use just a bucket and sponge".
The Irish Independent has reported that Irish Water believes that only a national ban on using hosepipes to water gardens, wash cars or fill paddling pools or ponds will help conserve supplies.
"Demand remains high, particularly during peak times, so we are still urging people to conserve water".
The release from Irish Water further explained: 'High levels of sunlight means significant evaporation levels on water sources.
On average demand across all water resources nationally has increased by 15%. Due to soil moisture conditions, smaller groundwater sites in particular may take many months to recover.
There is a "constant risk of restrictions" on the water supply in Mullingar and Athlone, Irish Water has said. 'Given the environmental pressures on the aquifers and waterbodies, this can not be sustained for any period of time, ' the statement further explains. It is the first time that Irish Water has imposed a nationwide ban. We are grateful for all measures that have been taken in homes and businesses, ' concludes the statement.
With no rainfall expected this week, the firm is encouraging its five million customers to use water more wisely in order to help ensure that the huge demand can continue to be met.
In a press release the company said that reports that that the supply/demand deficit in Westmeath and neighbouring counties could be be addressed by fixing existing infrastructure without the need for a new source of water in the short term is "misleading and does not reflect the reality of the situation facing the region". Similar drought orders have been introduced in Northern Ireland and in British water utilities and operate by mobilising public support for responsible behaviour.
Night-time restrictions are now imposed across more than 40 water supply schemes, with more than 100 more under threat.