Someone may use a basin or shower without realising it feeds the unit being worked on. That can introduce wastewater during an unsafe moment.
What the observation means
A notice on the toilet alone may be insufficient. The known connection list should be shared with everyone using the property.
A useful next step
Coordinate with the person carrying out service and keep all specified fixtures unavailable until released for use. Do not remove a notice because the pump briefly runs or appears quiet. Safe return to use depends on the agreed service process, not on a single sound.
Manuals and supporting guidance
Model-specific instructions take priority. These references support the practical principles discussed here; they do not diagnose your appliance.