• Stagnation in storage tanks promotes bacterial regrowth, including Legionella, when residual chlorine drops below safe levels

• Contamination events in building water systems can affect large numbers of occupants before detection

• Regulatory requirements for secondary water supply monitoring are tightening in many countries

• Maintenance access to rooftop tanks and underground reservoirs is limited — sensors must operate reliably for months between service visits

• Multiple monitoring points across a large building or campus require networked sensors with centralized data collection

Q: What residual chlorine level should be maintained in secondary supply tanks?

A: WHO guidelines recommend a minimum free chlorine residual of 0.2 mg/L at the point of use. In secondary supply systems with long residence times, maintaining 0.3–0.5 mg/L at the tank outlet is advisable to ensure adequate residual reaches distal taps. Levels below 0.05 mg/L should trigger an immediate investigation and corrective action.

Q: How can sensors be networked across multiple monitoring points in a building?

A: All Linksens sensors use RS-485 Modbus RTU, which supports multi-drop bus topology — up to 32 sensors on a single 2-wire cable run. This connects to a building management system (BMS) or IoT gateway for centralized monitoring and alerting, with no need for individual sensor power supplies at each monitoring point.