Axial vs Triplex Pump Pressure Washer: Which One Should You Buy?
Axial and triplex pump pressure washers compared for car washing: how each pump works, the pressure and flow each listing states, fit and upkeep, and which side suits each job.
On this page
Top picks at a glance
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- 1
Simpson PowerShot 4400 PSI Gas Pressure Washer9.7/10View on Amazon - 2
OEM Technologies 3400 PSI 2.5 GPM Horizontal9.5/10View on Amazon - 3
OEM Technologies 3300 PSI 2.4 GPM Horizontal9.5/10View on Amazon
Verdict: Choose an axial pump if you want a lighter replacement pump for a gas washer you already own and you wash cars and driveways at home. Choose a triplex pump if you wash for a living and want a complete washer with higher pressure and flow.
A car covered in road film and a driveway edged with grime both call for the same tool, and the pump inside the washer decides how that job goes. This comparison looks at axial vs triplex pump pressure washer designs, then at the listings behind each side, so you can match the pump to the work you do.
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Example pumps
Simpson PowerShot 4400 PSI Gas Pressure Washer
A 4400 PSI at 4.0 GPM gas pressure washer with a CRX 420cc engine, an AAA triplex pump, a 50-foot hose and 5 nozzle tips.
Pros
- 4400 PSI at 4.0 GPM from the AAA triplex pump
- CRX 420cc engine, PowerBoost for higher pressure at the nozzle
- 50-foot hose, 31-inch wand and 5 nozzle tips included
- Welded steel frame with 13-inch pneumatic tires
Cons
- No warranty term is stated
- 49-state compliant; does not ship to California
- A complete washer, so it needs more storage
- Fuel level must stay below the filler neck
OEM Technologies 3400 PSI 2.5 GPM Horizontal
A 3400 PSI at 2.5 GPM horizontal axial cam replacement pump kit with a 3/4 inch shaft, a maintenance-free crankcase and a thermal relief valve.
Pros
- 3400 PSI at 2.5 GPM for home washing jobs
- Maintenance-free crankcase, so no oil change is needed
- Anodized die-cast aluminum body with stainless steel pistons
- Thermal relief valve guards against overheating in bypass mode
Cons
- A replacement pump only, not a complete washer
- Fits horizontal engines with a 3/4 inch shaft only
- No hose, gun or wand is included
- Aimed at residential use rather than daily pro work
OEM Technologies 3300 PSI 2.4 GPM Horizontal
A 3300 PSI at 2.4 GPM horizontal axial cam replacement pump kit with a 3/4 inch shaft, a maintenance-free crankcase and a thermal relief valve.
Pros
- 3300 PSI at 2.4 GPM for home washing jobs
- Maintenance-free crankcase, so no oil change is needed
- Anodized die-cast aluminum body resists corrosion
- Thermal relief valve guards against overheating in bypass mode
Cons
- A replacement pump only, not a complete washer
- Fits horizontal engines with a 3/4 inch shaft only
- No hose, gun or wand is included
- Suits home washing rather than daily pro work
Side by side
| SIMPSON PowerShot PS60843 | SIMPSON OEM 90029 | SIMPSON OEM 90028 | |
|---|---|---|---|
| Pump type | AAA triplex plunger pump | Horizontal axial cam pump kit | Horizontal axial cam pump kit |
| Pressure | 4400 PSI | 3400 PSI | 3300 PSI |
| Flow | 4.0 GPM | 2.5 GPM | 2.4 GPM |
| Fit | Complete gas washer | Horizontal engines, 3/4 inch shaft | Horizontal engines, 3/4 inch shaft |
| Hose and wand | 50-foot hose, 31-inch wand | Not included | Not included |
| Nozzles | 5 nozzle tips | Not included | Not included |
| Warranty | Not stated | 2 year warranty | 2 year warranty |
| Weight | 61.23 kg | 7 pounds | 6 pounds |
We copy each listing’s rated specs exactly as the manufacturer gives them; as of 20 October 2026.
Axial vs triplex pump pressure washer: how each pump works
An axial cam pump sits in line with the engine shaft, and the listings here sell it as a replacement kit: a pump, hardware and a siphon tube, made to bring a gas washer back to life. A triplex plunger pump uses a crankshaft and a set of plungers, and the listing here sells it as part of a complete gas washer with a frame, hose, wand and nozzles.
Both axial kits share the same design: a maintenance-free crankcase, a body of fully anodized die-cast aluminum and a thermal relief valve. The SIMPSON OEM 90029 also lists stainless steel pistons. The triplex listing adds PowerBoost Technology, which the maker says delivers higher pressure at the nozzle.
Pressure and flow
Pressure and flow are the two figures every listing here states. The SIMPSON OEM 90029 is rated at 3400 PSI and 2.5 GPM, and the SIMPSON OEM 90028 is rated at 3300 PSI and 2.4 GPM. The SIMPSON PowerShot PS60843 is rated at 4400 PSI and 4.0 GPM, the highest pressure and flow stated in this comparison.
Those figures describe each listing only. The higher-rated PowerShot is the one the maker aims at contractors and long days of pro work, while the lower ratings suit home washing of walls, fences, sidewalks and vehicles, which is the use the 90028 listing names.
Fit and installation
Both axial kits use an SAE standard bolt pattern and fit horizontal engines with a 3/4 inch shaft, with a garden hose inlet and a threaded M22 high pressure outlet. Match engine orientation, pressure, flow, shaft diameter and the inlet and outlet connection before ordering; each kit includes hardware and a siphon tube.
The PowerShot needs no pump swap: it is a complete washer on a welded steel frame with 13-inch premium pneumatic tires, a 50-foot hose, a spray gun, a 31-inch steel wand and 5 quick connect nozzle tips. It is 49-state compliant and does not ship to California, so check that limit before ordering.
Durability and upkeep
The axial kits ask little upkeep: the crankcase is maintenance-free, so no oil change is needed, and the anodized die-cast aluminum body guards against corrosion. The SIMPSON OEM 90029 also lists stainless steel pistons, which the maker says improve seal life, and the thermal relief valve releases small amounts of hot water and intakes cooler water to prevent overheating while in bypass mode.
The triplex pump is also maintenance-free, with thermal relief, and its frame is welded steel with a powder coated finish.
Choose an axial pump if
- You already own a gas washer with a horizontal engine
- You want to replace a worn pump rather than buy a whole new washer
- You wash cars, walls, fences and sidewalks at home
- You want a pump kit with hardware and a siphon tube included
Choose a triplex pump if
- You wash for a living, or work long days on decks
- You want a complete washer with hose, wand and nozzles in the box
- You want the highest pressure and flow stated in this comparison
- You work across uneven ground and want pneumatic tires
For more choices, see the best pressure washer for engine bay, and the hot water vs cold water pressure washer comparison.
Keep electric pressure washers on a GFCI outlet, never point the wand at people or pets, wear eye protection with polishers and chemicals, and read the label before mixing any cleaning products. Read our Safety Disclaimer.
Garage Fit Check
- Match the axial kit to a horizontal engine with a 3/4 inch shaft and an SAE standard bolt pattern, and check the inlet and outlet connection before ordering.
- Allow floor space for the PowerShot frame and its 50-foot hose.
- The PowerShot is 49-state compliant and does not ship to California.
FAQ: garage tools
Is an axial or triplex pump better for washing a car?
It depends on the work. An axial pump suits home car washing, while a triplex pump suits pro work and long days of deck cleaning, wood restoration and paint preparation.
Can an axial pump kit replace the pump on a gas pressure washer?
Yes, if the kit fits: the listings here fit horizontal engines with a 3/4 inch shaft and an SAE standard bolt pattern. Match engine orientation, pressure, flow, shaft diameter and the inlet and outlet connection before ordering.
What does a thermal relief valve do?
It protects the pump from overheating while in bypass mode, releasing small amounts of hot water and taking in cooler water.
Does the Simpson PowerShot ship to California?
No. The listing states it is 49-state compliant and does not ship to California.
Related: the belt drive vs direct drive pressure washer comparison, the gas vs battery pressure washer comparison, the hot water vs cold water pressure washer comparison, and the best pressure washer for engine bay.
