MTH Pumps - ST21 Series

MTH Pumps ST21 Series DC Brushless Regenerative Turbine Pumps

  • Variable Capacities to 2 GPM

  • Heads to 450 Feet

  • Temperatures from -60° to 190°F

  • Stainless Steel Construction

  • Compact Size

  • Top Suction and Discharge

300 PSI Case Working Pressure

Rigid stucture is designed for maximum casing strength.

High Motor Efficiency

94% efficient permanent magnet motor minimizes heat input to fluid in heat sensitive applications like chillers and refrigerant handling.


ST21 Series pumps may be operated under adverse inlet conditions without audible or measurable cavitation.


Special inlet design provides superior fluid handling ability with low head inlet conditions.

100% Tested

Every pump is fully tested to verify performance prior to shipment.

Leak Free Sealless Design

Canned Sealless motor eliminates downtime, risk, and damage associated with mechanical seal failures. More compact and reliable than mag-drive solutions.

Versatile Motor and Controller

Integrated into the ST21 motor, a Variable Speed Controller accepts 115/230VAC or 12/24/48/100VDC power inputs and features variable speed output (2,000 - 10,000 RPM) that can be controlled via closed loop feedback from 4-20ma, 0-10VDC, or PWM transducers or other control circuitry.

Volatile Fluid Handling

The turbine impeller handles vapors up to 20% by volume, minimizing the possibility of vapor lock.

ST21 Performance Curves

(1) Stainless Steel Casing
(2) Stainless Steel Motor Bracket
(3) Stainless Steel Impeller
(4) Self-centering Balanced Impeller
(5) High Efficiency Water Channel Design
(6) “O” Ring Gaskets
(7) Long lasting Carbon Graphite/Ceramic Bearings
(8) Compact 115/230 VAC 12/24/48/100VDC Stator
(9) Integrated Variable Speed Controller
(10) Permanent Magnet Rotor
(11) Stainless Steel Rotor Retaining Sleeve
(12) High Strength Thermoplastic Liner

ST21 Dimensions

ST21 Options

Controllers available for 12/24/48/100 VDC or 115/230 VAC power. Controller options for manual speed control, external control via PWM, or closed-loop 0-10V or 4-20ma transducer speed control.

Pressure transducers and optional bearing and elastomer materials available upon request.

Future SC31 centrifugal version for capacities up to 15 GPM and Low NPSH applications.

Download a printable version of the ST21 Product Bulletin in .pdf format.

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