Lake Macquarie City Council will close Charlestown Swim Centre's 50-metre pool from Tuesday, March 26, until late May.

Council's leisure services manager Brendan Callander said the concrete sealing of the pool structure was due for renewal, requiring the entire pool to be drained and resealed.

"We know how popular Charlestown Swim Centre is, and how this will impact users of the 50-metre pool," he said.

"But we consulted with various user groups and stakeholders and concluded that this was the best time of year to do the work, with the minimum amount of disruption as a result."

Mr Callander said the maintenance was necessary to prevent chloride from the pool water seeping into the concrete, causing significant long-term damage.

"The closure period will allow for dispersal of chemicals in the pool water before the pool is drained and dried out in preparation for works," he said.

Charlestown Swim Centre's 25-metre pool and learn to swim pool will both remain open during the initial stage, but will close during resealing for public safety.

The entire swim centre is expected to be closed from Monday, April 15 to Friday, April 26.

"We've done everything we can to minimise that closure period and will be encouraging pool users to head to the city's other swim centres during that time," Mr Callander said.

The 25-metre pool and learn to swim pool are expected to reopen once the resealing has cured, but the 50-metre pool will remain closed until late May.