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1:128 Medicator | S128

The S128 Medicator or 1:128 Injection

  • Activated by a dry contact water meter
  • Doses into system flow rates up to 10 gpm
  • Automatically adjusts to system water flow

Flow Rate Outputs
10.0 ounces per minute up to 60 psi maximum
295.7 milliliters per minute up to 4.1 bar maximum


The S128 adjusts to the system flow rate for even distribution of product into the water line.

The S128 is designed to automatically inject solution into the water line proportional to the system water flow at a ratio of 1 ounce of solution to 128 ounces of process water. Activated by a dry contacting pulse water meter, the pump automatically adjusts to the water flow.

As the pump registers dry contacts, it delivers the precise ratio. The pump has three speeds to automatically adjust the injection rate when the water system flow rate increases or decreases. This flow response design allows the pump to evenly and proportionally inject solutions especially at low system flow rates. The S128 and the low flow VPD water meter are ideal for early stage poultry flocks and swine nurseries when water flow is minimal. The pump's relays allow use of an existing water meter and controller.

Injecting undiluted chemicals directly into the water line eliminates water restriction and the daily mixing of stock solutions. In addition, the pump is unaffected by poor water quality.


  • Potentiometer: Prime, 1 PPG, 1 PPL, 10 PPG, Reset Tube Timer, Standby
  • Output Relays: Signal Repeater Leak Detect, Drive Fault, Low Level
  • LED Indicators: Leak/Fault, Overrun, Change/Level, Power/Standby


    Built-in Signal Repeater Relay

    The built-in signal repeater relay allows an existing water meter to activate the pump and register water consumption with the house controller.

    Tube Change Timer

    Set the Tube Change Timer DIP switches with the number of hours you want the pump to run before the LED is activated. When the set time is reached the change/level LED is lit solid red. 
    The standby setting allows the tube replacement without disconnecting the pump.

    Leak Detect Setting & Relay

    Set the pump's DIP switch  to stop or to continue to run when a leak is detected. Set the optional output relay to notify another device if a leak occurs. 

    Signal Inputs

    The pump has three dedicated inputs to receive a signal from another device.
    1. Pulse Input: Receives a pulse from a dry contact water meter to activate the pump.
    2. Standby Input: The Standby Input can remotely start or stop the pump when a dry contact input is set to the pump.
    3. Level Input: Input from a fluid level device indicates a low level in the solution tank. The Level Input may be used with the low level output relay.

    Agency Approvals

    • cULus for indoor/outdoor use
    • NEMA 4X
    • NSF 61

    Advantages of All Stenner Peristaltic Pumps

    • Self-priming against max. working pressure; foot valve not required
    • Solutions do not contact moving parts
    • Pump head requires no valves, allows for easy maintenance
    • Does not lose prime or vapor lock
    • Pumps off-gassing solutions and can run dry.
    • Output volume is not affected by back pressure.
    • Simple tube replacement without tools

    Tube Replacement Video
    Chemical Resistance Guide

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    Flow Rate Output – 60 psi (4.1) max.

    Item No.
    per Minute
    per Minute
    Approximate Output @ 50/60Hz

    Maximum system water flow for 1:128 dosing is 10.0 gallons/minute or 37.9 liters/minute.

    exclamationNOTICE: The information within this chart is solely intended for use as a guide. The output data is an approximation based on pumping water under a controlled testing environment. Many variables can affect the output of the pump. Stenner Pump Company recommends that all metering pumps undergo field calibration by means of analytical testing to confirm their outputs.
    Flow Rate Output ControlPotentiometer
    Reproducibility+/- 2%
    Maximum Operating Temperature104°F (40°C)
    Maximum Suction Lift25 ft (7.6 m) vertical lift, based on water
    Motor TypeBrushless DC motor
    Duty CycleContinuous
    Maximum Viscosity1500 Centipoise
    Shaft rpm (average maximum)55
    Motor Voltage (Amp Draw)120V 60Hz 1PH (0.6)
    Power Cord Type120V 60Hz  SJTOWA
    Power Cord Plug End120V 60Hz  5-15P
    Cord Length6 ft (1.8 m)

    Materials of Construction 
    All HousingsPolycarbonate
    Pump TubeSantoprene®* (FDA approved)
    Ball Check Valve ComponentsCeramic ball (FDA approved); Tantalum spring; FKM seat & O-ring or
    Ceramic ball (FDA approved); Stainless steel spring; EPDM seat; Santoprene®* O ring 
    Pump Head RollersPolyethylene
    Roller BushingsOil impregnated  bronze
    Suction/Discharge TubingPolyethylene (FDA approved)
    Tube and Injection FittingsPVC or Polypropylene (both NSF listed)
    Connecting NutsPVC or Polypropylene (both NSF listed)
    Suction Line Strainer and CapPVC or Polypropylene (both NSF listed); ceramic weight
    All FastenersStainless steel
    Pump Head LatchesStainless steel
    Leak Detect ComponentsHastelloy®††

    Agency Listings

    * Santoprene® is a registered trademark of Exxon Mobil Corporation.
    †† Hastelloy® is a registered trademark of Haynes International, Inc

    Pump Dimensions


    Shipping Weight: 10 lbs (4.5 kg)

    Box Dimensions:  14 x 9 x 10 in. (35 x 23 x 24 cm)

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