The one working flume at the NSC will be out of action tomorrow night.
Government says it's as a manufacturer inspects both slides.
The flumes - which had been shut for more than three years for a multi-million pound revamp re-opened at the end of November last year.
However, by January 1 this year - one had closed.
Government said the closure followed concerns just before Christmas that 'the swimmer's exit from the flume wasn't always as smooth as it should be.'
The exact cause of the problem is yet to be established and still hasn't been fixed.