Brennan said the decision to immediately shut down the bore system was made to avoid damage to the plant and water temperatures had been slowing dropping since then.
"Re-casing the bores will involve inserting a new pipe of a smaller diameter inside the existing casing and then concreting this pipe into place," she said.
"This is expected to take three days, and the concrete will then need a four-day curing period."
Bay Venues hoped to switch the bore back on and start the heating process via a heat exchanger on May 29.
"The pools will then take at least 48 hours to reheat to normal temperatures," Brennan said.
The lap pool and wave pool will remain open for use and Brennan said swimmers were encouraged to bring their wetsuits to combat the cooler temperatures.
Brennan said the lap pool temperature was currently 23 degrees and was not expected to drop much further.
"The rate of temperature decrease in the lap pool has slowed significantly indicating that it may be levelling off as it approaches the ambient air temperature, although this will be dependent on the weather over the coming days," she said.