Authorities say that all traces of Legionella bacteria have been eradicated.
Beau Sejour was closed completely to the public last Tuesday (15 September) after Legionalla was discovered in the water system during routine testing the previous day.
It has taken six days to trace the outbreak, flush out the water system and sanitise it and order and fit new filters.
This work was overseen by experts in dealing with Legionella, often associated with large institutions.
The States say the task is mainly complete and the centre re-opened at 6.30am today (21 September).
Some areas have yet to have the new filters and taps fitted, and these are clearly marked as out of bounds.
The States asked anyone who had used the centre's showers and felt any respiratory problems to contact their GP as there was a possibility this could be Legionnaire's Disease, which is caused by Legionella.
Public Health has been monitoring this and as of the end of last week said no cases had occurred.
The six day closure has seen the cancellation of a UK tribute act and the annual dog show, both scheduled for the past weekend.
Beau Sejour remaining shut over weekend
Flyers advertising polar opposites delivered in Guernsey
Alex Scott named in England squad
Dangerous cycling on Guernsey roads
Closure ongoing at Guernsey's leisure centre
Guernsey's leisure centre closed for another day
Health authorities to consider 'cot cams' recommendation
Guernsey tax backlog 'worse than thought'
