Questions have been raised after the Papal Cross in Phoenix Park was washed down in the middle of a hose-pipe ban.
The Office of Public Works says the works were essential ahead of Pope Francis saying mass at the site next month.
Those in charge say the minimum amount of water required was used, and was drawn off before Irish Water put the current hose-pipe ban in place.
The Office of Public Works said the washing was "essential" to prepare for the painting of the cross, which hasn't been done in over four years.
"This event will be attended by approximately 500,000 people and viewed by millions from all around the world on television", a statement read.
It went on to confirm that "the contractor has indicated that no further water is required for the remainder of the works".
Irish Water has told people living in the Greater Dublin area that they cannot use hose-pipes to water their lawns or wash their cars during the heatwave.
It has been fighting to meet demand with shortages reported in a number of areas over the last few weeks, and some minor night-time restrictions being put in place.
Irish Water says it's asked Local Authorities to review maintenance activity involving high water use during the heatwave.