Tens of thousands of WA householders throw away money on water bills, with one in five homes in a trial of high-tech meters found to have leaky or defective plumbing.
Water Corporation chief executive Sue Murphy said the meters found "some sort of leak" for about 20 per cent of customers in the Kalgoorlie trial.
She told a parliamentary committee last week the leaks were only picked up because the "smart meters" detected water use that was hidden from the householder.
People might never find a cracked underground reticulation pipe but a smart meter would help locate it.
There were no figures for the rest of WA but they were likely to be similar for plumbing as old as in Kalgoorlie.
But Mrs Murphy was lukewarm about a wide rollout of the meters.
"It is very expensive," she said.
"When it is funded 50-50 with someone else, it stacks up, but the cost of a smart meter is more than 10 times a manual meter."