Independent Component Reference
Matching PSI and GPM is not enough—the shaft, flange, speed, ports and control system must also match.
This profile separates pump architecture, stated operating limits and exact integration checks so buyers can compare pressure-washer pumps without turning family-level data into a fit claim.
First published 2026-08-09 · Last verified 2026-08-09
Physical resemblance, matching wattage, matching voltage, a generic family name or a seller claim does not establish compatibility. Verify the current manufacturer part number and revision, machine model and serial scope, electrical and control specification, mechanical and fluid or airflow interfaces, protection requirements and approved service documentation.
| Fact | Technical reference | Scope boundary |
|---|---|---|
| Hydraulic output | Flow and pressure must be read at the stated pump speed and operating limit | Named product pages only. |
| Drive boundary | Gas-engine and electric-motor direct drives use different documented interfaces | The two named Cat Pumps families only. |
| Safety scope | Machine safety is wider than pump pressure capability | IEC 60335-2-79:2021 scope. |
Functional boundary
This WCB flow describes documented functions, not one universal product construction.
Receives shaft power at the specified speed, direction and mounting interface.
Named Cat and General Pump models.Sources: CAT 4DNX, CAT 4SP, General EZ4040
Plungers and valves displace water to create flow against system resistance.
Sources: CAT 4DNX, General EZ4040
An unloader or system control manages bypass and operating pressure; its inclusion varies by configuration.
Named official configurations only.Sources: General EZ4040, Comet zwd
Inlet condition, water temperature and allowed chemistry affect seals, valves and service life.
Exact model documentation controls.Sources: CAT 4DNX, General catalog
Architecture families
No architecture is a universal winner, and a family label is not a replacement-part specification.
Official Comet ZWD Series product image on a WCB canvas. Series membership does not establish an exact machine fit.
How to use this visualUse the photographed family only to understand documented construction context; do not infer exact product fit.
Official image sourceAR product-range families only.Sources: AR range
Sources: CAT 4DNX, General EZ4040, Comet zwd
Sources: CAT 4DNX, CAT 4SP, General EZ4040
Specification dictionary
| Specification | Purchasing meaning | Reporting boundary | Comparison caution |
|---|---|---|---|
| Maximum flow | Sets the documented volume boundary at the stated speed | GPM/LPM and rpm must remain paired | Do not compare flow without the stated pressure and speed. |
| Maximum discharge pressure | Sets the documented pressure ceiling | PSI/bar is a limit, not proof of continuous duty | Do not select only by the largest advertised PSI. |
| Pump speed | Controls the displacement rate and drive match | Maximum or rated rpm and rotation must be explicit | A lower engine or motor speed changes output. |
| Drive power | Supports engine or motor sizing at the specified operating point | GHP/HP/kW basis varies by source | Do not infer required power from pressure alone. |
| Shaft and mounting | Defines the mechanical coupling | Diameter, key, flange standard and orientation are separate fields | Physical resemblance does not prove interface equivalence. |
| Ports and inlet conditions | Defines plumbing, feed and cavitation boundaries | Thread standard, inlet pressure/vacuum and fluid temperature matter | Do not adapt ports without reviewing flow restriction and pressure rating. |
WCB reporting-boundary map: retain the stated unit, operating point, test method and product scope before comparing values.
How to use this visualKeep every reported value inside its stated unit, operating point, test method and product scope.
Diagram sourcesCAT 4DNX, General EZ4040, Comet zwd, IEC 60335 2 79
Use the exact source and current model documentation; field labels and test points vary by manufacturer.Sources: CAT 4DNX
Use the exact source and current model documentation; field labels and test points vary by manufacturer.Sources: General EZ4040
Use the exact source and current model documentation; field labels and test points vary by manufacturer.Sources: Comet zwd
Use the exact source and current model documentation; field labels and test points vary by manufacturer.Sources: IEC 60335 2 79
Use the exact source and current model documentation; field labels and test points vary by manufacturer.Sources: CAT 4DNX
Use the exact source and current model documentation; field labels and test points vary by manufacturer.Sources: General EZ4040
Evidence + WCB interpretation
Official application language narrows the review; it does not prove exact product fit.
Official General Pump EZ Series image on a WCB canvas, showing a gasoline-engine direct-couple family rather than a universal replacement.
How to use this visualTreat the photographed application as source context only. Verify the actual operating point, duty, envelope and approvals.
Official image sourceNamed families, not all engines.Sources: CAT 4DNX, General EZ4040
Candidate only when gasoline flange, shaft, rotation, rpm and required power are documented.
Sources: CAT 4SP
Requires the exact motor flange, shaft, speed, electrical duty and pressure-control design.
Sources: CAT pressure wash, IEC 60335 2 79
Triplex families may suit documented duty, but whole-system thermal and safety approval remains separate.
Compatibility gate
Physical resemblance, group ownership, generic family names, seller claims, and matching wattage do not establish compatibility.
WCB compatibility gate: an undocumented field stops approval rather than becoming a probable match.
How to use this visualPass every relevant gate using current manufacturer documents before approving a substitute, service part or design change.
Diagram sourcesCAT 4DNX, General EZ4040, Comet zwd, IEC 60335 2 79
Exact product and machine documentation controls.Sources: CAT 4DNX
Exact product and machine documentation controls.Sources: General EZ4040
Exact product and machine documentation controls.Sources: Comet zwd
Exact product and machine documentation controls.Sources: IEC 60335 2 79
Exact product and machine documentation controls.Sources: CAT 4DNX
Exact product and machine documentation controls.Sources: General EZ4040
Service boundary
Symptoms narrow inspection work; they are not a remote diagnosis or repair instruction.
Safety boundaryDepressurize and isolate the machine before inspection.
Service actionFollow the exact manufacturer's diagnostic and service procedure.
WCB inspection categories only; not a diagnosis for a specific machine.Sources: CAT 4DNX
Safety boundaryHigh-pressure fluid injection and hot surfaces are hazards.
Service actionRemove from service until the leak source and affected parts are identified.
WCB inspection categories only; not a diagnosis for a specific machine.Sources: General EZ4040
Safety boundaryStop operation before mechanical damage or loss of containment progresses.
Service actionVerify inlet supply, drive alignment, speed, oil and exact service limits.
WCB inspection categories only; not a diagnosis for a specific machine.Sources: Comet zwd
Representative, not exhaustive
These rows document manufacturer-published families. They do not establish a customer, OEM, factory or compatibility relationship.
| Manufacturer | Family | Architecture | Declared application | Distinguishing specifications | Scope |
|---|---|---|---|---|---|
| Cat Pumps | 4DNX25GSI | Triplex direct-drive plunger | Gas-engine pressure washing | 2.5 GPM · 3000 PSI · 3450 rpm | Global official product page |
| Cat Pumps | 4SP21ELU | Triplex direct-drive plunger | Electric-motor pressure washing | 2.1 GPM · 2000 PSI · 1750 rpm | Global official product page |
| General Pump | EZ4040G | Triplex gasoline direct-couple | Pressure cleaning | 4.0 GPM · 4000 PSI · 3400 rpm | US official product page |
| General Pump | TSF2021 | Triplex plunger | Professional pressure cleaning | Official catalogue family · Model-specific output table | Official catalogue |
| Comet | ZWD 4040 G | Triplex direct-drive | Gas pressure washing | 4.0 GPM · 4000 PSI · 3400 rpm | US official product page |
| Comet | EWD 4040 | Triplex direct-drive | Pressure washing | 4.0 GPM · 4000 PSI · 3400 rpm | US official application page |
WCB decision support
Named families, not all engines.Sources: CAT 4DNX, General EZ4040
Sources: CAT 4SP
Sources: CAT pressure wash, IEC 60335 2 79
Engineering validation
Series names can contain different outputs and configurations.
Required actionApprove manufacturer model, suffix and current revision before release.
Exact project, component and machine scope only.Sources: CAT 4DNX
Matching output numbers do not establish mechanical fit.
Required actionApprove shaft diameter, key, flange, rotation and coupling before release.
Exact project, component and machine scope only.Sources: General EZ4040
Flow and power change with speed.
Required actionApprove prime-mover rpm within the pump's documented limit before release.
Exact project, component and machine scope only.Sources: Comet zwd
Adapters can introduce restriction or pressure-rating risks.
Required actionApprove inlet/discharge threads, feed limits, hose and fittings before release.
Exact project, component and machine scope only.Sources: IEC 60335 2 79
Some configurations include controls and others do not.
Required actionApprove unloader, bypass, relief and injector arrangement before release.
Exact project, component and machine scope only.Sources: CAT 4DNX
Standards boundary
JurisdictionInternational
Version2021
ApplicabilitySafety requirements for high-pressure cleaners and steam cleaners within the standard's stated pressure, drive and application scope.
Standard scope only; no product certification is inferred.Sources: IEC 60335 2 79
JurisdictionUnited States
VersionCurrent edition must be checked
ApplicabilityReferenced by UL guide information for electrically operated high-pressure cleaning machines; no product certification is inferred.
Standard scope only; no product certification is inferred.Sources: UL 1776
JurisdictionEngine interface
VersionCurrent revision must be checked
ApplicabilityGeneral Pump identifies the named EZ family flange as SAE J609B; verify both engine and pump documentation.
Standard scope only; no product certification is inferred.Sources: General EZ4040
Technical developments
The reviewed official range separates many pump series by architecture and operating envelope.
Named publication or reviewed official portfolio only.Sources: AR range
The edition updates the safety scope and alignment for high-pressure cleaners.
Named publication or reviewed official portfolio only.Sources: IEC 60335 2 79
Audit trail
Last material modification 2026-08-09 · Last verified 2026-08-09
Cat Pumps
Accessed 2026-08-09
Open sourceCat Pumps
Accessed 2026-08-09
Open sourceCat Pumps
Accessed 2026-08-09
Open sourceGeneral Pump
Accessed 2026-08-09
Open sourceGeneral Pump
Accessed 2026-08-09
Open sourceComet
Accessed 2026-08-09
Open sourceComet
Accessed 2026-08-09
Open sourceAnnovi Reverberi
Accessed 2026-08-09
Open sourceIEC
Accessed 2026-08-09
Open sourceUL
Accessed 2026-08-09
Open source