Description
The JS Pumps GST-12 (code 020-712) is the smallest pump in the three-phase GST grinder range. A 1.2 kW, 400v motor drives a cutter against a high-chrome grinder ring, shredding soft solids so the pump can deliver up to 190 litres per minute and lift to 19 metres of head through a 1¼” outlet.
It is the three-phase version of the single-phase GS-1200, so choose it when you have a 400v supply. If you need more lift on the same 1¼” pipe, the GST-15 reaches 22 metres. For a larger inflow, the 2″ GST-22 moves up to 320 litres per minute.
The pump body, impeller, oil chamber and motor covers are cast iron, the motor case and shaft are stainless steel, and the cutter and grinder ring are high-chrome cast iron. The mechanical seal is silicon carbide and carbon, running in an oil chamber, and the motor has a built-in overload protector. JS Pumps offers the pump free standing or guide rail mounted, so it can sit on a coupling foot and be lifted out of the chamber for servicing. The outlet is 1¼” (32 mm) and the pump comes with 10 metres of power cable.
Features
- 1.2 kW motor, 400v three phase
- Up to 190 l/min and 19 m head
- 1¼” (32 mm) outlet for small-bore rising mains
- High-chrome cutter and grinder ring, rated by JS Pumps at up to 28,000 cuts per minute
- Cast iron pump body and impeller, stainless steel motor case
- Silicon carbide and carbon mechanical seal in an oil chamber
- Free standing or guide rail mounted
- 10 metres of power cable
Applications
- Houses and annexes on a three-phase supply with a long run to the sewer
- Basement toilets and washrooms below sewer level
- Small workshops and outbuildings needing a sewage sump
- Small package sewage stations with a control panel
Designed for sewage and waste water containing soft solids. Not suitable for sand, gravel, stones or other hard debris, which wear or jam the cutter, or for oils, solvents, chemicals or flammable liquids. It has no float switch, so it needs a three-phase control panel with level control.

The JS GST grinder range
| Model | Supply | Outlet | Motor (kW) | Max Flow (l/min) | Max Head (m) | Code |
|---|---|---|---|---|---|---|
| GST-12 | 400v 3 phase | 1¼” | 1.2 | 190 | 19 | 020-712 |
| GST-15 | 400v 3 phase | 1¼” | 1.5 | 190 | 22 | 020-715 |
| GST-22 | 400v 3 phase | 2″ | 2.2 | 320 | 23 | 020-720 |
| GST-37 | 400v 3 phase | 2″ | 3.7 | 330 | 36 | 020-737 |
Flow and head are maximums read from the performance curve above. See the JS GST grinder sewage pump range page for help choosing between models, or the JS GS range for single-phase versions.









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