Product Description

The SIMPSON ALH3425 Aluminum 3600 PSI 2.5 GPM Professional Gas Pressure Washer is engineered for contractors, property-maintenance professionals, and demanding users who need substantially more durability and cleaning performance than a typical residential pressure washer.

Producing up to 3600 PSI at 2.5 gallons per minute, the ALH3425 combines strong cleaning pressure with useful water flow for tackling stubborn dirt, grime, weathering, and other demanding exterior-cleaning jobs. SIMPSON specifically positions the Aluminum Series for professional applications such as deck cleaning, wood restoration, paint preparation, graffiti removal, and other professional cleaning services.

At the heart of the machine is a premium Honda® GX200 gasoline engine. This professional-grade engine includes a low-oil shutdown feature, which helps protect the engine when the oil level becomes unsafe for continued operation. The GX200 is paired with a direct-drive pump configuration for a compact and efficient power-transfer system.

Water pressure is generated by a heavy-duty AAA® triplex plunger pump. Unlike lighter-duty axial-style pump systems commonly used on entry-level machines, the triplex design is intended for more demanding cleaning duty. The pump includes an integrated unloader and thermal relief valve to help manage pressure and pump temperature during operation.

One of the ALH3425’s standout design features is its high-grade aircraft-aluminum frame. The aluminum construction gives the pressure washer a combination of strength, corrosion resistance, and reduced weight compared with many conventional steel-frame designs. SIMPSON lists the complete unit at approximately 78 lb.

The washer comes equipped with a 35-foot MorFlex® high-pressure hose. The 5/16-inch hose is designed to be flexible, abrasion-resistant, and non-marring, giving the operator useful working range while reducing the need to continually reposition the pressure washer.

A professional spray gun with M22 connection is paired with a quick-connect spray lance. Five quick-connect nozzle tips are supplied, giving the operator a choice of 0°, 15°, 25°, 40°, and soap spray patterns. This makes it easy to adapt the machine from concentrated high-pressure cleaning to wider general-purpose rinsing and detergent application.

Mobility is handled by 10-inch premium pneumatic tires, helping the washer move over driveways, yards, construction areas, and other uneven working surfaces more easily than a small hard-wheel configuration.

With professional Honda power, a service-oriented AAA triplex pump, aircraft-grade aluminum construction, a 35-foot hose, and a complete five-nozzle cleaning setup, the SIMPSON ALH3425 is built as a serious cold-water cleaning system for demanding residential and professional environments.

Key Features

3600 PSI Professional Cleaning Pressure

Delivers up to 3600 PSI for removing stubborn dirt, grime, buildup, and surface contamination.

2.5 GPM Water Flow

A maximum 2.5 GPM flow rate combines with the high-pressure output for efficient professional cleaning performance.

Honda GX200 Engine

Premium Honda® GX200 gasoline power provides dependable performance for demanding cleaning applications.

Low-Oil Shutdown

The engine incorporates low-oil protection designed to shut the engine down when the oil level becomes unsafe.

AAA Triplex Plunger Pump

Professional AAA® triplex pump technology provides high-pressure water delivery and is equipped with an integrated unloader.

Thermal Relief Valve

The integrated thermal relief system helps protect the pump against excessive heat buildup.

Aircraft-Grade Aluminum Frame

High-grade aluminum construction is lightweight, durable, and resistant to corrosion.

35-Foot MorFlex Hose

The included MorFlex high-pressure hose provides extended reach while remaining flexible, abrasion-resistant, and non-marring.

Five Quick-Connect Nozzles

Includes 0°, 15°, 25°, 40°, and soap nozzle tips.

10-Inch Pneumatic Tires

Large pneumatic tires help improve maneuverability across different working surfaces.

These features are all listed by SIMPSON for manufacturer Part No. 60689.

Technical Specifications

Official dimensions, weight, hose, nozzle, pump and engine information are published directly in SIMPSON’s current specifications.

Pump Configuration

Pump Brand: AAA®
Pump Type: Triplex Plunger Pump
Drive Configuration: Direct Drive
Maximum Pressure: 3600 PSI
Maximum Water Flow: 2.5 GPM
Unloader: Integrated
Thermal Relief Valve: Included

The professional triplex pump configuration is one of the major differences between the ALH3425 and lighter residential pressure-washer platforms. Its integrated unloader manages pressure while the thermal relief system provides additional pump protection.

Cleaning Attachment Configuration

0° Red Nozzle

Provides a highly concentrated spray pattern for tough cleaning where an intense stream is appropriate.

15° Yellow Nozzle

Provides a narrow fan pattern suitable for stronger general cleaning.

25° Green Nozzle

Offers a medium-width spray pattern for many routine pressure-washing applications.

40° White Nozzle

Provides a wider fan pattern for lighter cleaning and rinsing.

Soap Nozzle

Designed for low-pressure detergent application.

The ALH3425 includes all five quick-connect tips as standard equipment.

Hose & Spray System

High-Pressure Hose: MorFlex®
Length: 35 Feet
Diameter: 5/16 Inch
Gun Connection: M22
Spray Lance: Quick-Connect
Hose Characteristics: Flexible, abrasion-resistant and non-marring

The long hose provides useful working range around buildings, vehicles, driveways, decks, equipment, and other cleaning areas without requiring constant machine repositioning.

What’s Included

The standard SIMPSON ALH3425 / Part No. 60689 configuration includes:

• 1 × SIMPSON ALH3425 Aluminum Series Pressure Washer
• 1 × Honda® GX200 Gasoline Engine
• 1 × AAA® Triplex Plunger Pump
• 1 × 35-Foot MorFlex® High-Pressure Hose
• 1 × Professional High-Pressure Spray Gun with M22 Connection
• 1 × Quick-Connect Spray Lance / Wand
• 1 × 0° Quick-Connect Nozzle
• 1 × 15° Quick-Connect Nozzle
• 1 × 25° Quick-Connect Nozzle
• 1 × 40° Quick-Connect Nozzle
• 1 × Soap Quick-Connect Nozzle
• 2 × 10-Inch Premium Pneumatic Wheels/Tires
• Aircraft-Grade Aluminum Frame
• Manufacturer Documentation