The Sewer Choke is jammed
The first sign of a problem will frequently be that, when flushing the toilet, the water backs up to the rim of the bowl and does not drain away. A sewer choke or surcharge is happening when raw sewage starts to overflow from any toilet or floor waste outlet in your bathroom, laundry or kitchen. It may also overflow from a ground level vent pipe outside a ground floor apartment. In the event of an overflow you should contact your strata manager to have the matter inspected.