The Wanganui East pool continues to lose water at the rate of 30,000 litres a day but no one has a clue where it's going.
The Wanganui East Pool Trust, which is managing the complex, says it is not drawing the water. The Wanganui District Council says, in that case, it's a mystery.
But come April 30, when the trust's contact expires, council staff will be able to undertake a thorough investigation.
The startling numbers were delivered at the council's operations and reporting committee meeting this week.
Committee chair Councillor Ray Stevens said technical investigations had been carried out on the pool's infrastructure and pipes but no significant problems were found.
"I don't know what else we can do," Mr Stevens said. "The trust says it's not drawing water off the city supply and that amount of water can't just evaporate every day. There's got to be something else wrong here, that's for sure.
"It's five months since the pool re-opened for this season. Losing 30,000 litres of water day means it's going to cost council $45,000 assuming the contract runs through until the end of April."
Mr Stevens said he hoped that the trust would "pull the pin" on the baths if temperatures and patronage dropped, even before the contract expired.
The problems at the pool came to a head last year when it was found that almost 18 million litres of water had been lost in the first six months of 2013.
Council officers told the committee this week that in spite of temporary repairs being carried out before it opened last December, the complex had been using 30,000 litres a day.
"At the end of this season the council's plan is to take back control of the complex with the pools remaining full so that we can undertake a full review of the water usage and define where the loss is occurring, something which currently we aren't able to do," he said.
The pool's future is bleak. Engineering assessments say it is nearing the end of its economic life. It would cost at least $3.5 million to build a new outdoor complex.