Stenner S128 Series Proportional Medicator Pumps
The Stenner S128 Series is a flow-responsive peristaltic medicator designed to proportionally inject chemicals at a fixed 1:128 ratio, delivering 1 ounce of solution for every gallon of process water. Activated by a dry contact pulse water meter, the S128 automatically adjusts to changing water demand and provides accurate dosing for livestock water treatment, agricultural applications, and other proportional injection systems.
Unlike traditional medicators, the S128 uses a peristaltic pump design and automatically varies pump speed to maintain even chemical distribution, particularly at lower flow rates. The pump can inject into water systems with process flows up to 10 GPM while maintaining the target dosing ratio.
Flow-Responsive Proportional Injection
The S128 is designed to work with:
- 1 PPG water meters
- 10 PPG water meters
- 1 PPL water meters
The pump automatically changes between three operating speeds based on system flow rate, helping provide more consistent solution distribution across varying flow conditions.
Key Features
- Fixed 1:128 dosing ratio
- Up to 10 oz/min output
- Water meter activated operation
- Built-in signal repeater relay
- Leak detection with output relay
- Tube change timer and reminders
- Low-level tank input
- Remote standby input
- NEMA 4X enclosed housing
- Indoor/outdoor rated construction
- Brushless DC motor
- Continuous-duty operation
- 2-year warranty
Built-In Monitoring and Protection
The S128 incorporates several maintenance and protection features to help improve reliability and reduce downtime.
Leak Detection
- Detects solution inside the pump head
- Can be configured to stop or continue pump operation
- Activates a dedicated relay output
Tube Change Timer
- Programmable tube replacement reminder
- Adjustable in 100-hour increments
- Dedicated LED indication when service is required
Signal Repeater Relay
- Repeats incoming water meter pulses
- Allows one meter to operate the pump and a controller simultaneously
- Eliminates the need for a second water meter in many applications
Dedicated Inputs and Outputs
The pump can receive signals from:
- Dry contact pulse water meters
- Low-level tank sensors
- Remote standby controls
Built-in relay outputs support:
- Signal repeating
- Leak detection
- Drive fault indication
- Low-level indication
Typical Applications
- Poultry water treatment
- Livestock health programs
- Agricultural chemical injection
- Waterline disinfection
- Proportional medicating systems
With flow-responsive dosing, integrated monitoring features, and reliable peristaltic pump technology, the Stenner S128 Series provides accurate proportional injection for demanding agricultural and water treatment applications.

