Hanna Instruments pH / ORP / Temperature Swimming Pool & Spa Dosing Controller (In-Line, 115/230V) (BL121-10)

Hanna Instruments pH / ORP / Temperature Swimming Pool & Spa Dosing Controller (In-Line, 115/230V)

The BL121-10 is a wall-mounted, all-in-one dosing controller designed to maintain safe, balanced water quality in swimming pools, hot tubs, and spas. It simultaneously monitors pH, ORP (redox), and temperature via a single combined digital probe installed directly in-line with your existing pipework, then automatically doses acid and chlorine through two built-in peristaltic pumps. Supplied as a complete, ready-to-install kit, it is the straightforward in-line configuration of the BL121 platform.

Measurement & dosing performance

The controller measures pH from 0.00 to 14.00 (±0.05 pH accuracy), ORP from ±2000 mV (±5 mV accuracy), and temperature from -5.0 to 105.0 °C, all from a single HI1036-1802 combined digital probe. Both pH and ORP dosing are proportionally controlled with adjustable set points and proportional bands, and an ORP dosing consent feature ensures chlorine is never dosed until pH is correctly balanced first — preventing chemical waste and unsafe chlorine spikes. Overdosing protection and a power-on delay add further safety.

Logging & alarms

Readings of pH, ORP and temperature are logged automatically, together with calibration data and alarm events. Programmable high/low alarms make the BL121-10 suitable for attended and unattended pool plant rooms.

What’s in the box

The BL121-10 ships as a complete installation kit: the BL121 controller unit, an HI1036-1802 combined pH/ORP/temperature digital electrode with 2 m cable, electrode saddle and injector saddles for Ø 50 mm pipe, two injectors, 5 m of peristaltic pump injection tubing, replacement pump tubing (×2), suction filters (×2), pH 4.01 and 7.01 buffer sachets (3 × 20 ml each), a 470 mV ORP reference solution (250 ml), and a power cable — everything needed to commission the system from scratch.