Siptu officials will meet management at Irish Water later after the company announced bonuses are being put on hold.
The performance-related payments for 2013 and 2014 are now subject to a review.
The union represents about a quarter of Irish Water employees.
Spokesman Adrian Kane isn't ruling anything out when it comes to fighting his members' corner at Irish Water.
He said: "What's always open to trade unions is the withdrawal of labour, or the use of the industrial relations machinery provided by the State.
"As I would see it, I don’t want to see banner headlines in terms of a 'Strike is imminent at Irish Water', we'll meet with the company.
"We're not accepting unilateral changes and we'll have to decide and we'll be mandated by our members."