Minister for Communications, Energy and Natural Resources Alex White has announced the membership of the board of Ervia, which has overall responsibility for Irish Water and Gas Networks Ireland.
However, the Government has also confirmed that the two subsidiaries will also have "small executive boards to directly manage their businesses".
Last year, Minister for the Environment Alan Kelly said the board of Ervia and the board of Irish Water would merge.
In relation to the board of Ervia, four members are being retained: Chairman Rose Hynes, CEO of Ervia Michael McNicholas, Mari Hurley and Finbarr Kennelly.
Separately, SIPTU General Secretary Joe O'Flynn has been reappointed for three years.
Four new members have been appointed today; Sean Hogan, who is Northern Irish Water chairman, James Martin, Celine Fitzgerald and Peter Cross.
They have been appointed for five years.
The board of Ervia will be increased later to 11 members.
Under Department of Public Expenditure and Reform rules, the chair is paid €31,500 and a board member is paid €15,750.
Separately, the Irish Water board will comprise of Mr McNicholas, with executive directors John Tierney, Irish Water Managing Director; Michael G O'Sullivan, Ervia's Chief Finance Director; and Brendan Murphy, who is Ervia's Director of Group Commercial and Regulation.
Mr McNicholas will also chair the board of Gas Networks Ireland.
It will have three executive directors, and Mr Murphy is on this board as well.
The two other members are Michael O'Sullivan, Ervia's Chief Financial Officer, and Sean Casey, Managing Director of Bord Gáis Networks.
The Department of Communications said that the boards of Irish Water and Gas Networks Ireland have four members each, are made up of internal managers and they are not paid.
A spokesman said Mr White made a statement on the structure last November.
A spokesperson for Ervia said as Irish water and Gas Networks Ireland are registered companies, they must have directors and these directors will form an internal management board but the board of Ervia has overall responsibility.
Another Government spokesperson pointed to a similar board structure in the CIE group.