Applicabilty of gst on water charges and sewerage charges for a commercial society

There is a commercial society. It has been collecting water charges for tenants who have used more than the allotted quantity of water per month, should it charge GST for these water charges.

similarly, it has been charging sewerage charges for certain restaurants where it has to clear the clogged drain on a weekly basis. Does it need to charge GST for this also.

In case it has to charge GST in the above 2 cases , what will do the charges applicable.

Kindly advise