
Hanna Instruments Pool and Spa Controller BL-121-10
The BL-121-10 Pool and Spa Controller offers automatic control of pH and Chlorine levels in swimming pools, hot tubs and spas. An inline system, it allows for direct installation of probe and chemical injection fittings into existing piping. Professional installation required.
BL-121 is a new high performance hygiene control system for swimming pools, hot tubs and spas. It combines quick and easy monitoring for pH, ORP and temperature together with automatic chlorine dosing.The controller is available in two versions:
- Inline system (BL-121-10) allows for direct installation of probe and chemical injection fitting into existing piping.
- Optional bypass flow cell included (BL-121-20) - ease of maintenance enhanced by allowing calibration and maintenance of the probe without the need to shut down the recirculation pump
Key features:
Multi-coloured LED indicators for dosingMeter status and service
USB Connectivity
Real-time graph display
Automatic logging
Programmable alarms
Password protection
Specifications
pH range:0.00 to 14.00pH
pH Resolution: 0.01pH
pH Accuracy (@25°C: +-0.05pH
pH Calibration: pH buffer calibration automatic, two-point (4.01, 7.01, 10.01pH); pH process calibration: one-point, manual input
pH Dosing: Proportional with adjustable set point and proportional band; delay to start at power-on and overdosing protection
mV range: +-2000mV
mV Resolution: 1mV
mV Accuracy @ 25°C: +-5mV
ORP (mV) calibration: one-point, manual input
ORP Dosing: Proportional with adjustable set point and proportional band; delay to start at power-on and overdosing protection; pH dosing interlocked
°C range: -5.0 to 105.0°C
°C Resolution: 0.1°C°
C Accuracy @25°C: +-1°C
Temperature Compensation: automatic, -5.0 to 105.0°C for pH
Pump control: Automatic and manual modes; adjustable flow rate from 0.5 to 3.5L/h
Log feature: Automatic logging of pH, ORP, and temperature measurements, GLP and events including alarms, errors, and power failure; capacity for 60 days with 10 seconds sampling interval; all data.csv files are transferred by USB flash drive
Alarms: High and low with enable/disable option for all parameters; alarm is triggered when 5 consecutive readings are over/under threshold
Alarm System: Intuitive alert system based on LEDs; alarm filtering options; alarm relay control based on user set up
Password Protection: Set up, calibration and log recall options features are password protected
Storage interface: USB
GLP: pH/ORP calibration information including date and time for pH/ORP sensors
Alarm Relay Output (1): SPDT 5A/230 VAC; activated by pH/ORP/temperature selectable alarm conditions
Analogue Outputs (3): 4 to 20mA, sourcing configurable; output impedance ≤ 500
Ohm; accuracy < 0.5 % FS; galvanically isolated up to 50 V relative to earth ground
Auxillary Inputs (2): Low level in acid/base tank (contact open); low level in chlorine tank (contact open); hold input (contact open)
Digital Probe input (1): Galvanic isolated digital input HI-1036-1802 pH/ORP/temperature/matching pin combined probe with DIN waterproof connector
Power supply:100-240 VAC
Power consumption: 10 VA
Environment: 0 to 50°C, max 95% RH non-condensing
Dimensions: 245 x 188 x 55 mm (73mm with pumps)
Weight: 1700g
Sku:BL-121-10

Frequently Asked Questions
Clear answers to help you choose the right water testing solution with confidence
Which brands of water testing kits do you supply?
Do you provide kits for both home and professional use?
Yes — whether you’re a pool or spa owner, aquarium keeper, utility company, or a university laboratory, we have the right solution for your needs.
Can I arrange servicing or calibration for my photometer?
Absolutely. We also provide servicing and calibration to keep your photometers accurate and reliable.
How quickly do you dispatch orders?
Orders placed before 2:30 pm (Monday–Friday) are dispatched the same day. We also ship on Saturdays for your convenience.
Which couriers do you use for delivery?
We deliver through UPS, DPD, and Royal Mail. You can also choose to upgrade to next-day delivery at checkout.
What is your return policy?
We accept returns within 14 days of delivery provided the items are unused, in their original packaging, and in resalable condition. Please contact our team before returning any items.
Can I place bulk or business orders?
Yes, we welcome bulk, trade, and institutional orders. For tailored pricing or large quantities, please get in touch with us directly.
How can I get help if I’m unsure which kit to buy?
You can call us at 📞 +44 (0)115888 2726 and our team will guide you in choosing the most suitable kit for your needs.