More than a million dollars in back pay is expected to be awarded to youth workers at the Adelaide Youth Training Centre who remained on duty during their lunch breaks, following a decision by the South Australian Employment Tribunal.

Key points: Adelaide Youth Training Centre staff are expected to receive more than a million dollars in backpay

The SA Employment Tribunal found they had been underpaid because they had not been able to take their entitled breaks

The case could set a precedent for other employees who are expected to work through their meal breaks

The tribunal's deputy president, Stephen Lieschke, ruled that three youth workers had been underpaid since October 2015 because they had not been able to take their entitled breaks while on the job.

He upheld the workers' claims for penalty rates to apply after five hours of continuous work without a break.

The tribunal heard that the workers were expected to spend their meal times monitoring detainees as they ate their meals.

The workers told the tribunal that they had to be extra vigilant during meal times as tensions could escalate quickly and they needed to make sure detainees did not assault anyone with a knife or fork.

One of the workers described meal times as the "highest risk time" during his whole shift.

Public Service Association General Secretary Nev Kitchin welcomed the tribunal's ruling.

"It was a great outcome," he said.

"It's a situation where these people were monitoring young residents who were in a custodial environment and under the work health and safety act and of course the Enterprise Bargaining Agreement they should have been having their break."

The tribunal heard the claims of three workers as a test case out of 124 workers in total who lodged similar claims.

"We need to remember though that this has been going on some time prior to 2015 as well," Mr Kitchin said.

"One could argue that the government has been saving a lot of money prior to that."

The decision could be used as a precedent for other public sector employees who are expected to take breaks while remaining on duty.

"There are other areas where this is occurring and when our members bring it to our attention then we would naturally investigate and take the appropriate action," Mr Kitchin said.

The State Government argued that the workers were not underpaid because they were subject to a working arrangement that provided for recognised paid "crib breaks" on each shift.

It argued that there was no minimum time limit for a crib break and even if a youth worker ate an apple while on duty, they were still having a crib break.

Deputy President Lieschke will hear submissions on the exact amount of compensation at a later date.