A Hamilton City Councillor has slammed the way Waikato Hospital treated his son who went missing on unescorted leave and was latter found dead.

Nicholas Stevens drowned in the Waikato River two weeks ago.

The 21-year-old was a patient at Waikato Hospital's Henry Bennett Centre.

Councillor Dave Macpherson says his death was totally avoidable.

"They've let Nicholas down, they've let us down all along the way. Our biggest regret, to be honest is that we somehow thought he would be safe in the Henry Bennett centre."

At a health board meeting today Hamilton City Councillor Dave Macpherson, supported by his wife and son, asked the board to pay for expenses they'll incur in a Coroners Inquest and Health and Disability Commission investigations.

The 21-year-old was patient at Waikato Hospital's Henry Bennett Centre when he was found dead in the Waikato River.

Mr Macpherson says it's not a level playing field.

"We don't have the resources that the hospital has to fund their representation so we're asking that they fund us to the same level that they're funding themselves."