Every household in the country has been sent information about getting setup with the new water authority including getting an online account and paperless billing.
They’re using water.ie
But they do not control water.ie – it’s not registered to them and never has been. Irish Water is a subsidiary of Bord Gais but it’s a separate legal entity, so it would make more sense if the domain name was registered to them and not the “parent”. After the amount of public criticism levelled at the entity I’m sort of surprised that Bord Gais haven’t wanted to distance themselves even further. See here for example.
So what about the domain? It’s registered to Bord Gais Eireann:
% Rights restricted by copyright; http://iedr.ie/index.php/mnudomregs/mnudnssearch/96
% Do not remove this notice
descr: Bord Gais Eireann
descr: Statutory Body
descr: Discretionary Name
person: Barry Murphy
person: Help Desk Support
Based on data from HosterStats it looks like the domain has moved around a few times over the years, but has always been hosted by companies that generally serve semi-state bodies.