How to Install a Pressure Washer Chemical Injection Kit



This DIY repair guide explains how to replace a pressure washer chemical injection valve. The chemical injection valve draws detergent into the pump when you use a low-pressure nozzle for cleaning. A worn or damaged chemical injection valve won’t pull detergent into the water stream. If the pressure washer isn't spraying soapy water when it should, first make sure you’re using a low-pressure nozzle and the siphon hose isn’t clogged. If so, replace the damaged chemical injection valve with the manufacturer-approved replacement kit. The chemical injection kit includes the O-ring and all parts needed for the repair.

Follow the steps in this repair guide to install the chemical injection kit in common Craftsman, Generac, Briggs & Stratton, Husqvarna and Troybilt pressure washers.

Repair difficulty:
Time required:

Less than 15 min.

Parts Required

  • Chemical injection kit

For manuals, repair guides, and specific part recommendations, enter your model number.

Tools Required

  • Metric wrench set
  • Silicone lubricant
  • Torque wrench (optional)
  • Work gloves

Before you begin

Wear work gloves to protect your hands.


 Warning: Undertaking repairs to appliances can be hazardous. Use the proper tools and safety equipment noted in the guide and follow all instructions. Do not proceed until you are confident that you understand all of the steps and are capable of completing the repair. Some repairs should only be performed by a qualified technician.

Step 1: Disconnect the spark plug

Disconnect the spark plug wire from the spark plug.

Step 2: Remove the chemical injection valve

If detergent is in the detergent reservoir, clamp the chemical injection hose near the chemical injection valve.

Use an open-end wrench to turn the chemical injection valve counter-clockwise and remove it.

Step 3: Install the new chemical injection valve

Install the O-ring from the kit on the new chemical injection valve.

Lubricate the O-ring with silicone lubricant. Thread the new chemical injection valve into the pump and tighten. Reconnect the chemical injection hose.

Release the clamp from the chemical injection hose, if used.

 Tip: If you have a torque wrench, tighten the new chemical injection valve to 10-12 ft.-lbs. or torque.

Step 4: Reconnect the spark plug

Reconnect the spark plug wire to the engine.

Step 5: Check pressure washer operation

Start the pressure washer and check for leaks.

Check for proper detergent draw through the new chemical injection valve.