Local authority staff may strike over plans for a mass transfer of 3,500 of them to Irish Water.
Delegates at a Fórsa conference will debate a motion that hints at industrial action if terms and conditions - including a 40km limit on their relocation distance from work - worsen.
Numerous motions have been tabled calling for an early date for a constitutional referendum on the ownership of the water service.
A motion, tabled by the Mayo Health and Local Government Branch, today calls on the union to "defend resolutely" their terms and conditions "by all means at our disposal".
The chair of Fórsa's Local Government and Local Services division, Seán Reid, said last year Irish Water outlined its intention to create a single water agency and employer by 2021.
Meanwhile, Mr Reid said the Citizens' Assembly should be used to develop meaningful local government reform.
He said research commissioned by Fórsa showed only 8pc of Irish public spending occurs at local government level.
This compares with an EU average of over 23pc.
"It also contributes to declining local election voter turnout," he said.
"With little more than two weeks to go before polling day, this is sobering and dispiriting for those of us who've committed our careers to local democracy," he added.