Someone who left a hosepipe running cut off the supply of water to 90 people and four businesses.
The incident happened on Thursday to customers of Irish Water in Kirikee, Co Wicklow which is just outside Greystones.
Engineers discovered that water levels in the local reservoir, which were already low because of the prolonged period of dry weather over the summer, had fallen considerably.
The source of the leak was discovered to be a local householder who had left a hosepipe on overnight.
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A garden hose can flow at 20 litres per minute or about 1,200 litres per hour. Over the course of a day a garden hose can use the equivalent daily supply for 230 people.
A tanker was brought into the area and it took between two and three hours to restore normal supply to 35 homes and four businesses affected by the leak.
Irish Water spokesman Kevin Love said the use of the hosepipe had been “excessive and non-essential” and it demonstrated the extent to which even one individual can affect water supply.
“We are appealing to everyone to continue playing their part in helping to conserve water, and particularly to avoid non-essential use such as running hoses or power washers,” he said.
In nearby Rathnew the water supply was affected when a member of the public used fire hydrants for purposes other than fire fight for which they are intended.
Mr Love warned: “Misuse of fire hydrants has the potential to put lives in danger and prolong or extend damage to premises in the event of an incident where water is unavailable due to unauthorised use.
“In the current extreme weather conditions, misuse is impacting Irish Water’s ability to meet customers’ water supply needs.”
The majority of Irish Water’s 750 water treatment plants continue to meet the demand for water supply but there are 49 supplies nationwide that are being impacted by drought conditions.
These include West Cork, where a Water Conservation Order is in place, as well as parts of Tipperary, Limerick, Wexford, Waterford and Galway.
Irish Water has been managing supplies by bringing water to reservoirs by tanker. However, in some areas such as Clonakilty, Co Cork and parts of South Tipperary, night time restrictions and/or pressure reduction have been put in place to protect supplies.