If the success of a water recycling trial is anything to go by, Perth residents could soon be drinking water that was once sewage.

A three-year trial of groundwater replenishment was completed by the Water Corporation at the end of 2012 with what Water Minister Bill Marmion has called "excellent preliminary results."

More than 2.5 billion litres of recycled water was "recharged" during the three-year trial.

The water that went through the system started out as water that went down sinks, was used in washing machines, or flushed down toilets.

That water is usually processed at Beenyup Wastewater Treatment Plant and pumped out to the ocean, but as part of the trial a small portion of it was treated through three further steps.

While the water processed as part of the trial was restored to drinkable standards, as it was just a trial, it was not put back into Perth's drinking water system; instead it was pumped into the Leederville aquifer.

Mr Marmion said more than 70,000 water quality results obtained throughout the trial had met stringent health and environmental guidelines for drinking water.

"Based on the trial's positive outcomes, the Water Corporation has been given an interim go-ahead by regulators to continue operating and recharging water at the purpose-built recycling facility," he said.

More than $100 million was allocated in the State Budget's forward estimates to expand the trial plant to a seven billion litres of water per year capacity.

A decision to move to a full-scale scheme is dependent on the final assessment of the trial.

Groundwater replenishment could be progressively expanded over a 10-year period to the full capacity of the Beenyup Wastewater Treatment Plant of 28 billion litres per year

Water Corporation and trial regulators, the Department of Health, Department of Water and Department of Environment and Conservation will spend the next four months completing a detailed assessment of the trial.

The State Government will then review this assessment, and consider the viability of groundwater replenishment as a future climate independent water source for Perth.

Each day 335 million litres of waste water is created in Perth.