Work is continuing on modifications at Walton on the Naze Lifestyles in a bid to get the site reopened as soon as possible.
However, Tendring District Council is now aiming for mid-February rather than the end of this month as had previously hoped for.
Once the scheme is completed it will need to be followed by a series of water tests, each of which will be required to incubate for 14 days for results to be confirmed.
Only when all the test results come back negative for Legionella will the facility be reopened to the public.
The building on the Esplanade was shut at the end of last year due to a discovery of the bacteria.
Carter Environmental Ltd was brought in to carry out a comprehensive survey of the water system.
The water treatment specialist firm provided TDC with a report and the alterations, based on those recommendations, are well underway.
Lynda McWilliams, TDC’s Cabinet Member for Leisure Health and Wellbeing, said it has taken longer than first expected and apologised to customers and thanked them for their loyalty.
“The safety of our customers is – and always has been – the paramount consideration in the reopening of this site,” she said.
“The improvements have been carried out as quickly as possible but it takes as long as it takes and we must get this absolutely right.
“We really do appreciate the patience of our customers and we ask them to bear with us just a little longer. We are aiming to reopen in mid-February but it is difficult to predict an exact date right now.”
Letters will be sent to those customers who pay by direct debit to let them know that payment will not be taken for February to compensate for January.
Those who pay annually will have the time the facility remains closed added to the end of the membership period. All direct debit and annual customers can still access other TDC sites during the closure at no cost.