Important Safety Information
WARNING:
This product produces high pressure. Always follow proper handling and usage instructions to prevent injury. Never point the nozzle at people or animals. Always wear appropriate personal protective equipment when using this product. Never mix chemicals in the tank. Always clean the sprayer after use and dispose of any remaining solution responsibly. Always follow the manufacturer's instructions for proper maintenance and disposal.
Product Overview

Front view of the SOLO 425-HD Backpack Sprayer, showing the white tank with "SOLO 425-HD HEAVY-DUTY Made in USA" branding, the black lid, pump handle, and spray wand with nozzle.
Key Features:
- High-performance piston pump for liquid formulation.
- Adjustable pressure regulator with four settings: 15, 30, 45, 60 psi.
- Durable professional grade brass adjustable, brass fan, hollow cone, jet stream nozzles.
- No-drip check valve eliminates nozzle drip after pressure is released.
- Viton seals in critical locations for superior chemical resistance.
- Extra large carrying handle with wand retainers for easy portability and storage.
- Deluxe shoulder straps and waist belt for user comfort.
Setup and Assembly
Before first use, ensure all components are securely attached and properly assembled. Refer to the included diagrams for visual guidance.
- Attach Shoulder Straps and Waist Belt: Connect the deluxe shoulder straps and waist belt to the designated attachment points on the sprayer frame. Adjust for a comfortable and secure fit, ensuring the weight is evenly distributed across your back and hips.
- Connect Hose and Wand: Securely attach the spray hose to the pump outlet and the spray wand to the hose handle. Ensure all connections are tightened to prevent leaks.
- Install Nozzle: Select the desired nozzle (brass adjustable, brass fan, hollow cone, or jet stream) and screw it firmly onto the end of the spray wand.
- Inspect Seals: Verify that all seals, especially the Viton seals, are properly seated and free from damage. This ensures superior chemical resistance and prevents leaks.

A person wearing the SOLO 425-HD Backpack Sprayer, demonstrating how the shoulder straps and waist belt distribute weight for user comfort during operation.
Operating Instructions
Follow these steps for safe and effective operation of your SOLO 425-HD Backpack Sprayer.
- Prepare Solution: Carefully mix your desired liquid formulation according to its manufacturer's instructions. Never mix chemicals directly in the sprayer tank.
- Fill Tank: Unscrew the tank lid and pour the prepared solution into the 4-gallon tank. Do not overfill. Securely fasten the lid.
- Pressurize Sprayer: Place the sprayer on your back using the shoulder straps and waist belt. Operate the pump handle with a steady, rhythmic motion. The unique fluid-driven pump design will pressurize the tank to working pressure with as few as eight to ten strokes. Continue pumping until the desired pressure is achieved.
- Adjust Pressure (Optional): The adjustable pressure regulator offers four settings: 15, 30, 45, and 60 psi. Adjust the regulator as needed for precision application.
- Begin Spraying: Point the nozzle towards the target area and depress the trigger on the spray wand handle. Release the trigger to stop spraying. The no-drip check valve prevents dripping after pressure is released.
- Maintain Pressure: Periodically pump the handle during operation to maintain consistent pressure for optimal performance.
Maintenance and Storage
Proper maintenance ensures the longevity and optimal performance of your sprayer.
- Cleaning After Use: After each use, thoroughly clean the sprayer. Empty any remaining solution responsibly according to local regulations. Rinse the tank, hose, and wand with clean water. Pump clean water through the system to flush out any residue.
- Inspect Seals and O-Rings: Regularly inspect all seals and O-rings, especially the Viton seals, for wear or damage. Replace them if necessary to prevent leaks and maintain chemical resistance.
- Nozzle Care: Clean nozzles regularly to prevent clogging. If a nozzle becomes clogged, remove it and clean it with water or a soft brush. Do not use metal objects that could damage the nozzle orifice.
- Lubrication: Periodically apply a silicone-based lubricant to the pump piston and O-rings to ensure smooth operation and extend their lifespan.
- Storage: Store the sprayer in a clean, dry place, away from direct sunlight and extreme temperatures. Ensure the tank is empty and clean before storage. The extra large carrying handle with wand retainers aids in compact storage.
Troubleshooting
Refer to this section for common issues and their solutions.
| Problem | Possible Cause | Solution |
|---|---|---|
| No pressure or low pressure |
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| Leaking from connections |
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| Nozzle dripping after release |
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Specifications
| Attribute | Detail |
|---|---|
| Brand | SOLO |
| Model Name | Backpack Sprayer w/ handle |
| Item Model Number | 425-HD |
| Tank Volume | 4 Gallons |
| Material | HDPE, Polyethylene, Steel, Brass |
| Item Weight | 11.03 pounds (5.01 Kilograms) |
| Product Dimensions | 9.5"W x 21"H |
| Power Source | Manual |
| Included Components | Pump, Hose |
| Maximum Pressure | 90 PSI (9E+1 Pound per Square Inch) |
| UPC | 720343425772 |
Warranty and Support
SOLO products are manufactured by Solo, Inc. For specific warranty details, please refer to the documentation included with your purchase or visit the official SOLO website.
Protection plans are available for extended coverage. For assistance with product operation, maintenance, or troubleshooting beyond this manual, please contact SOLO customer support. Keep your model number (425-HD) and UPC (720343425772) ready when contacting support.
For more information, you may visit the SOLO Store on Amazon.





