Thousands of businesses in the greater Dublin area are set to be hit with higher water charges because of a move to a standard national charge rate.
At present, Dublin businesses pay lower rates than others.
Irish Water chief John Tierney said: "At the moment you have a number of different charges because you have 34 different local authorities.
Some are higher, some are lower. The understanding is that over time that will move to a standard charge so obviously some will go up and some will go down. Some people will pay more."
The final decision on the amount homeowners will have to pay will be made by the end of August, but some public consultation will take place in June, Mr Tierney said.
The proposed charge will be assessed by the Commissioner for Energy Regulation who will then hold a public consultation.