Irish Water is lowering the city's water pressure at night to conserve supplies.
It says it can sustainably and safely produce 610 million litres of water per day.
But in the past 24 hours, it says this reached 615 megalitres.
"This level of demand meant drawing from treated water storage to maintain full supply", the company says.
"This option can only be maintained for a limited period of a few weeks.
"This record level of summer consumption is also depleting raw water reserves needed for the coming months."
It says the lowered night time levels "will not impact businesses but will assist Irish Water managing demand more effectively."
Its Drought Management Team is meeting daily and monitoring supplies and demand.
But the utility is "very concerned" about the possibility of having to impose long term restrictions.
It says this will be "unavoidable" if the dry conditions continue into the autumn, with lower than normal rainfalls.