Many municipal water systems operate with small teams—sometimes only a few technicians overseeing multiple stations across vast geographic areas.
To your question, why are PLCs connected to the internet? I can think of the following reasons:
24/7 Alerts: Remote connectivity allows engineers to receive instant alerts on mobile devices or home terminals if a pump fails, a chemical level drops, or pressure spikes outside normal thresholds.
Off-Hour Management: Without remote access, utilities would need round-the-clock, on-site staffing at every pump house, booster station, and treatment facility, dramatically increasing labor costs.
Diagnostic Speed: Vendors often demand remote access (via VPNs, cellular gateways, or remote desktop tools) to diagnose glitches or adjust configurations without dispatching a field technician.
Enterprise Integration: Utility business networks (IT) need operational data from plant floors (OT) for billing, inventory forecasting, and compliance dashboards.
Cloud SCADA/Telemetry: Smaller utilities increasingly use cloud-hosted SCADA platforms or IoT sensors to manage data storage and reporting, which inherently relies on internet connectivity.
In many cases, PLCs were never intended to be directly exposed to the public internet, but end up exposed due to networking mistakes.
I can do all of the above without exposure. (I design PLCs)