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Pressure Washer Spray Gun Replacement

Whether you use an electric or gas-powered pressure washer to power wash your vehicle, driveway, deck, or home siding, the spray gun, or trigger handle, is the component that releases the water pressure built-up by the pump and allows you to direct the high-pressure water stream so it will impact on the area you need it to. A malfunctioning spray gun/trigger handle can be replaced, but you’ll want to make sure it’s the handle itself that is defective and not one of the other pressure washer components.

How does the pressure washer and its spray gun work together?

Electric pressure washers use a motor to drive the pump while most gas-powered washers will use a 4-cycle engine. The pressure washer pump consists of three plungers or pistons that operate in a similar manner to a piston in an engine. As each plunger or piston travels upward, it draws water from an attached garden hose through an input check valve. As the plunger or piston travels downward, the water is forced through an output check valve. The water then flows through an unloader and output pipe on the pump, and then through a hose to the spray gun. When the spray gun trigger is depressed, the pressurized water will exit through the trigger handle assembly itself or through a separate spray wand and nozzle.

When the trigger is released, the high-pressure water stream should stop. The unloader will then detect the increase in pressure and a spring-loaded valve will open a passage in the pump so the water can circulate back to the inlet pipe. This feature allows the engine to run while the pressure washer is not in use.

Troubleshooting and maintenance tips

Problems that occur with pressure washers are often the result of insufficient water pressure or the operator not purging the air from the pump before operation. When air is compressed inside the pump, the check valve, plungers or pistons, and unloader can become damaged which results in pressure loss and leaking. Other tips you should be aware of:

  • Be sure to only use a dedicated high-pressure hose to connect the inlet pipe to the spray gun. The hose’s pressure rating should be higher than the pressure washer pump, which can typically be 1,300 psi to 1,700 psi for electric models and 2,000 psi to 3,200 psi for gas-powered models.
  • If you’re using a chemical injection system to add detergent to the water stream, you will need to use a low pressure nozzle to properly draw the detergent into the hose.
  • Consider using a pump lubricant like Pump Saver to help protect the plungers or pistons, as well as the seals on the pressure washer when it’s in storage.

Replacing the spray gun/trigger handle

While the procedure for replacing a defective spray gun/trigger handle with a new one is fairly simple, it can vary depending on the pressure washer model. Here are some general steps you should follow:

  • Confirm that the motor or engine is not running and any excess water has been purged from the system.
  • Detach the high-pressure hose from the trigger handle.
  • If applicable to your model, unthread the spray wand and nozzle assembly from the trigger handle.
  • Before you install the new trigger handle, apply some lubricant to the handle’s O-ring, if relevant to your model.
  • If applicable, thread the spray wand into the new handle.
  • Confirm the high-pressure hose O-ring is intact and apply some lubricant to the O-ring.
  • Thread the high-pressure hose onto the new trigger handle.
  • Once installed, start up the pressure washer and confirm the new spray gun/trigger handle is working properly.

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