Wellington Water has set the scope for its independent inquiry into the capital's fluoridation

Fluoride had been turned off at the Te Marua plant last May - and at the Gear Island plant in November.

That means Upper Hutt, Porirua and Wellington City haven't had fluoride in their water for months.

The probe will look at management's failure to inform necessary parties of issues ... in an accurate and timely manner.

Wellington Water board chair Lynda Carroll says it's a step to clarifying the situation.

The final report is due by May 31.