The new system divides uniformed officers into two teams � response teams and local policing teams (LPT).
Union representatives recently visited all Perth police stations and found LPT members appeared to be happy, but identified pressures with the response teams.
Union president George Tilbury said response members were �under immense pressure and battling to keep up with demand�.
Response teams only attend urgent matters, such as domestic disputes, whereas LPT officers have an investigative role in following up the issues in the days after the initial response.
Mr Tilbury said the response team concept �appears to be working�, but there were not enough officers to manage it.
�If immediate changes are not made, burnout will occur,� he said.
Concerns were highlighted when a response team constable wrote a letter to the union, saying the role had become �constant drama� and �seriously relentless�.
In the letter, the officer wrote there was no respite from stressful situations, whereas under the old system � when officers were not split into teams � they would attend a mix of less demanding jobs and urgent matters.
�The balance is gone. It�s all or nothing now,� he wrote in the letter.
But Insp Lewis� outlook of the situation was more positive.
He said officers in the district were this month offered the option to transfer to new positions if they were uncomfortable with the roles they had been given when the model came into effect in December last year.
He said fewer than 2 per cent of officers from more than 500 in the district had asked for a transfer, but it was not because they were experiencing stress in their roles.
Despite the claims of pressure in the response teams, he emphasised one officer had requested to join the response unit. He said two response team constables had left their roles, but did so because they wanted to take on investigative positions with the local policing teams in the hope of becoming detectives.
Two response team sergeants also requested a transfer, but Insp Lewis said it was because of career opportunities and a desire to work closer to home.
He pointed to the small number of transfers � and the fact the officers had not based their requests on stress � as evidence there was no major issue with the new model.