The head of Irish Water’s parent company has announced his resignation from the role.
Michael McNicholas was appointed CEO of Ervia in May 2013, having previously served as chief executive of wind energy company NTR.
He cited personal reasons for his decision to step aside.
Ervia said its board will now begin the process of seeking a suitable candidate to succeed Mr McNicholas, who has set a date of May 2017 for his exit.
The company's chairman, Tony Keohane, said he had made an "enormous contribution" to its work.
"While we respect Michael’s decision, we very much regret losing someone of his calibre from our organisation," he said.
"Michael has played a key role in the establishment of Ervia and has led the company through its complex and demanding evolution from its origins as Bord Gáis Éireann.
"That journey involved the sale of the Bord Gáis Energy business, the formation of Gas Networks Ireland and the creation of Irish Water.
"Under Michael's leadership, Ervia has built a high quality team that has continued to develop the state’s gas network and made very significant progress towards the required transformation and rehabilitation of the Ireland's water and wastewater infrastructure."
Mr McNicholas said: "The decision to leave Ervia has not been an easy one.
"While my time at the company has been very challenging, it has also been very rewarding.
"I have had the privilege of working with exceptional people who have given everything they can to make this company successful.
"Indeed many have gone far beyond what is reasonable to expect, and I and the board of Ervia owe each of them a debt of gratitude.
"There are many reasons to stay, not least the tangible benefits of the hard work of this great team that are beginning to come to fruition.
"My reasons for leaving are purely personal. There are other opportunities I wish to explore in my career and personal life and this decision affords me the time and space to do this."
Ervia, formerly known as Bord Gáis Éireann, employs over 1,300 staff nationwide.
The semi-state company was renamed in June 2014 following its sale to Centrica plc.
