Reviewed July 21, 2026
Before you begin
High-pressure spray can penetrate skin. Shut down, turn off water, and squeeze the trigger to relieve pressure before service.
Start here
Decide whether pressure was low from startup or dropped after normal operation. These have different likely causes.
Water supply
- Open the supply valve fully and verify inlet flow meets the washer requirement.
- Inspect the garden hose for kinks or collapse and clean the inlet screen.
- Purge air using the manufacturer's startup procedure before running the pump.
Technical reference: Simpson pressure-washer troubleshooting manual
Nozzle, gun, and hose
- A detergent or low-pressure nozzle will not create cleaning pressure.
- Shut down and use the manual's nozzle-cleaning procedure; never look into the nozzle.
- Replace damaged high-pressure parts rather than patching them.
Technical reference: Simpson pressure-washer troubleshooting manual
Pump direction
- Confirm the engine reaches specified operating speed before blaming the pump.
- For pulsation, recheck inlet restriction, trapped air, and nozzle blockage first.
- If pressure declined after normal use, seals, valves, or the unloader may require pump-specific service.
Technical reference: Simpson pressure-washer troubleshooting manual
Stop and reassess when
- A high-pressure hose, gun, fitting, or pump casting is damaged.
- Water has entered electrical parts.
- Internal pump work lacks exact documentation and tools.