Grundfos DMX 221-B Mechanical Diaphragm Dosing Pump

The Grundfos DMX 221-B Mechanical Diaphragm Dosing Pump is a robust, industrial-grade dosing solution designed for applications where simple, dependable chemical dosing is required without electronic controls or signal inputs. Built for continuous duty in demanding environments, the DMX series is driven by a mechanically coupled AC motor and precision gearbox, delivering reliable, repeatable dosing performance.

Unlike digital dosing pumps, the DMX 221-B uses mechanical stroke length adjustment, allowing flow to be set manually via an easy-to-adjust control knob. This makes the pump ideal for installations where constant dosing is required and simplicity, durability, and serviceability are priorities.

The dosing head features a PVC liquid end, PTFE-coated diaphragm, and ceramic ball valves, providing excellent chemical resistance and long service life for common water treatment and industrial chemicals. The rugged thermoplastic pump housing and IP65 motor enclosure ensure reliable operation in harsh plant environments.

Available in multiple flow and pressure configurations, and in both single-phase and three-phase power options, the Grundfos DMX 221-B is well suited to water treatment plants, industrial process dosing, and OEM skid systems requiring a proven mechanical dosing pump solution.

APPLICATIONS

• Water and wastewater treatment chemical dosing
• Industrial process water treatment
• pH correction and chemical conditioning
• Cooling tower and boiler water treatment
• OEM dosing skids and packaged systems
• Applications requiring constant, fixed-rate dosing
• Harsh environments where electronic controls are not required

FEATURES

• Mechanical diaphragm dosing pump with external AC motor
• Manual stroke length adjustment (mechanical control)
• Robust gear-eccenter drive system for long service life
• PVC dosing head suitable for common treatment chemicals
• PTFE-coated diaphragm for chemical resistance and durability
• Ceramic ball valves for accurate, repeatable dosing
• Thermoplastic pump housing for industrial environments
• Simple, reliable design with minimal maintenance requirements
• IP65 motor enclosure
• Available in single-phase and three-phase power options

SPECIFICATIONS

Performance

• Maximum flow: 16–115 LPH (variant dependent)
• Maximum pressure: Up to 12 bar
• Stroke adjustment range: 1:10
• Dosing accuracy: ±1.5% (FS)
• Linearity: ±4% (FS)
• Maximum viscosity: 200 mPas

Hydraulic

• Liquid temperature range: 0 to 40 °C
• Maximum suction lift: Up to 4 m
• Maximum permissible inlet pressure: 0 bar

Materials

• Pump housing: Thermoplastic
• Dosing head: PVC
• Diaphragm: PTFE-coated
• Valve balls: Ceramic (Al₂O₃)
• Valve seat / gaskets: EPDM

Electrical

• Supply voltage:
  • 1 × 220/240 V, 50 Hz
  • 3 × 230/400 V, 50 Hz
• Power input: ~0.09 kW
• Enclosure class: IP65
• Frequency converter: Not prepared for VFD

BENEFITS

• Extremely reliable mechanical dosing with no electronics
• Ideal for constant-flow, continuous dosing applications
• Simple setup and adjustment via manual stroke control
• Excellent chemical resistance for common treatment media
• Long service life with minimal maintenance
• Suitable for harsh industrial environments
• Available in both single-phase and three-phase configurations
• Proven Grundfos industrial dosing design