Hanna Instruments pH/ORP/Temperature Swimming Pool Controller with Panel-Mounted Flow Cell (BL121-20)

Hanna Instruments pH/ORP/Temperature Swimming Pool Controller with Panel-Mounted Flow Cell

The BL121-20 is a complete, panel-mounted dosing controller for swimming pools, hot tubs, and spas that continuously measures and automatically controls pH, ORP (chlorine/redox), and temperature. It is the flow-cell variant of the BL121 series, supplied as a ready-to-install kit including the HI1036-1802 combined digital probe, a panel-mounted bypass flow cell, chemical injectors, pipe saddles, dosing tubing, calibration solutions, and a power cable. Unlike the in-line BL121-10, the BL121-20 routes a water bypass through a dedicated flow cell, making probe calibration and maintenance straightforward without stopping the recirculation pump.

Panel-mounted flow cell design

The BL121-20 mounts on a panel and uses a bypass flow cell to sample pool water continuously. This design allows technicians to service or calibrate the HI1036-1802 pH/ORP/Temperature digital probe at any time without interrupting pool circulation. The flow cell configuration is the recommended choice for professional installations where minimising downtime is critical.

Intelligent dosing & control

Two built-in peristaltic dosing pumps deliver pH-correction and chlorine chemicals with proportional control — dosing time is automatically adjusted as a percentage of the deviation from the setpoint, providing precise, stable water chemistry. An ORP dosing consent feature prevents chlorine from being dosed until the pH value has first been corrected, avoiding chemical waste and unnecessarily high chlorine concentrations.

Data logging & alarms

All pH, ORP and temperature readings are logged automatically, together with calibration data and alarm events, and programmable alarms warn when a value leaves its range.