51.0401.09 InterpumpGroup W1210 Piston D. 18x25: Complete Buyer's Guide for Worldwide Sourcing
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The 51.0401.09 InterpumpGroup W1210 piston D. 18x25 is the correct replacement piston for Interpump W1210-series high-pressure pumps where the plunger diameter is 18 mm and the assembly length is 25 mm. It restores lost flow and pressure caused by plunger wear, and it is ordered by pump model plus diameter — never by SKU alone.
What is the 51.0401.09 InterpumpGroup W1210 piston D. 18x25?
A 51.0401.09 InterpumpGroup W1210 piston D. 18x25 is a precision-ground plunger assembly used inside Interpump W-series positive-displacement high-pressure pumps. The "D. 18x25" designation means an 18 mm plunger diameter in a 25 mm assembly envelope.
Interpump Group is the dominant OEM for industrial plunger pumps in pressure-washing, reverse-osmosis, misting and process-water duty. Because the piston is a wear part, it is replaced on a service interval rather than at pump end-of-life.
Quotable definition
A 51.0401.09 InterpumpGroup W1210 piston D. 18x25 is an 18 mm diameter replacement plunger assembly for Interpump W1210 high-pressure pumps, restoring rated flow and pressure (typically up to 200 bar / 2,900 psi) after wear. It is a service spare, not a standalone pump.
How does an Interpump W-series piston work?
The piston reciprocates inside a ceramic or hardened-steel liner, drawing water through an inlet valve and displacing it through an outlet valve on each stroke. Sealing is achieved by a high-pressure packings set that bears against the plunger surface.
When the plunger surface scores, pits or wears oval, the packings can no longer seal, and the pump loses pressure and flow. Replacing the piston restores the seal interface — provided the packings and valves are replaced at the same time.
Spec table: 51.0401.09 W1210 piston D. 18x25
| Attribute | Value |
|---|---|
| OEM part reference | 51.0401.09 |
| Pump family | Interpump W1210 |
| Plunger diameter | 18 mm |
| Assembly length | 25 mm |
| Typical rated pressure | 200 bar (2,900 psi / 20 MPa) |
| Typical rated flow | 15 L/min (3.96 US gpm) |
| Typical rotation regime | 1,750 rpm |
| Typical drive power | 5.73 kW (7.8 hp) |
| Typical pump weight | 9.5 kg |
| Typical pump envelope (L x W x H) | 273.5 x 223 x 152.5 mm |
Values above reflect the W1210 pump class the piston serves. Confirm against your pump nameplate before ordering — Interpump uses the same part number across several plunger diameters.
Which Interpump pump models use this piston?
The W1210 piston family is used across Interpump's W-series and closely related T-series pumps. If you are replacing a piston, it is usually more economical to confirm the whole pump model and order the matching service kit.
For higher-duty applications, buyers often step up to a larger Interpump pump rather than repeatedly rebuilding a small one. The table below shows the ladder from compact to heavy-duty Interpump pumps stocked by 3G Electric.
Product selection ladder: Interpump pumps and spares
| Model | Flow | Pressure | Power | Rotation | Best for |
|---|---|---|---|---|---|
| Inter[[PRODUCT:TS1331-000|pump TS1331 | 13 L/min | 120 bar | 2.94 kW | 1,450 rpm | Light-duty washdown, intermittent duty |
| Inter[[PRODUCT:T01321-000|pump T1321 | 15 L/min class | 200 bar class | 5.73 kW class | 1,750 rpm | General industrial pressure washing |
| Inter[[PRODUCT:T09281S0U-000|pump T9281 L | Mid-range | High-pressure class | Mid-range | 1,750 rpm | Continuous process duty |
| Interpump T2830Y SX Pump with 53R Motor | 30 L/min (7.92 US gpm) | 275 bar | 15.44 kW (21 hp) | 1,750 rpm | Heavy-duty continuous industrial duty |
| Inter[[PRODUCT:AB0150CD-000|pump AB150 PTO R | PTO-driven | Agricultural class | PTO-driven | Tractor PTO | Agricultural spraying, field service |
Step up the ladder when duty cycle exceeds 50% or when pressure demand exceeds 200 bar. Step down when the pump runs intermittently and weight or cost is the constraint.
Supporting spares and accessories
- Interpump FOAMKIT 3 for T/TX Series Pumps — foam injection for cleaning applications
- Interpump VARIOJET Kit with 125 Nozzle — adjustable nozzle kit
- Interpump Flexible Coupling 56C — motor-to-pump coupling
How to select the right piston: 6-step checklist
- Read the pump nameplate — record the full model (e.g. W1210) and serial.
- Confirm plunger diameter — 18 mm in this case; do not assume from the pump model alone.
- Check the assembly length — 25 mm here; mismatched length will not seat correctly.
- Inspect packings and valves — replace them with the piston to avoid repeat failure.
- Verify operating pressure and flow — 200 bar / 15 L/min is the W1210 class envelope.
- Confirm supply voltage and frequency for the drive motor — 50 Hz and 60 Hz ratings differ, so specify both when ordering a pump-plus-motor package.
Worldwide sourcing considerations
3G Electric supplies the 51.0401.09 piston and the wider Interpump range to buyers worldwide on incoterms-neutral terms — EXW, FOB, CIF or DDP as required. Export documentation (commercial invoice, packing list, certificate of origin) is prepared as standard.
For cross-market installations, confirm motor nameplate voltage and frequency: a 50 Hz-rated pump package will deliver different flow at 60 Hz, and vice versa. Specify the target grid when ordering a pump-plus-motor assembly.
Why source from 3G Electric
3G Electric stocks 4,007 products across 14 industrial departments — machining, electrical, power transmission, material handling, plumbing, HVAC & refrigeration, pneumatics, hydraulics, pumps, instrumentation, test & measurement, welding, lighting and combustion. Our specialist depth in pumps, combustion and controls means we interpret your demand and deliver the right part, not just a part number.
With 35+ years of experience, we support sizing, cross-referencing and technical queries before you order. We are a distributor and supplier — not an authorised dealer — and we are accountable for every part we ship.
Key takeaways
- The 51.0401.09 piston fits Interpump W1210 pumps with an 18 mm plunger and 25 mm assembly length.
- Always confirm pump model, plunger diameter and assembly length before ordering.
- Replace packings and valves with the piston to avoid repeat failure.
- Step up to a larger Interpump pump when duty cycle exceeds 50% or pressure exceeds 200 bar.
- 3G Electric supplies worldwide with export documentation and technical support.
Get a quote
Contact 3G Electric for pricing, sizing assistance and technical support on the 51.0401.09 InterpumpGroup W1210 piston D. 18x25 and the full Interpump pump range. Send your pump nameplate details and we will confirm the correct part.
