The workers have between 11 and 30 years' experience each, with some aged in their 60s.

The plumbers' union believes they are set to receive six-figure payouts.

Communications, Electrical and Plumbing Union state secretary Rodney Burles said the workers were given assurances that their jobs were safe when they switched from the Launceston City Council to the water corporation in 2009.

``You'd think after so many years of service you'd be shown a bit of dignity,'' Mr Burles said.

Mr Burles estimates that redundancies, first reported in December, could cost taxpayers and ratepayers more than $500,000.

``This is only going to drive up the cost of your bill,'' Mr Burles said.

A Fair Work Commission conference will consider the issue tomorrow in Launceston.

A spokeswoman for Ben Lomond Water said that the company was working through the consultation process with Fair Work Australia.

The union will argue that the consultation is not legitimate, and has vowed to fight the decision.

The workers were told of the decision to make the construction crew redundant on February 22. The redundancies are due to take effect from March 28.

The three state water corporations will merge in July.