A pressure washer chemical injector pulls detergent or soap into the water stream when the machine is running in low-pressure mode. When the injector becomes clogged, corroded, damaged, or worn internally, the pressure washer may stop drawing soap or may leak water from the injector nipple. Before ordering a replacement injector, always confirm the correct part number using the pump model number and parts breakdown.
In this video, we show how to install a chemical injector on an AAA 8.7GA12 triplex plunger pump using the 7104228 Simpson & AAA Pump Chemical Injector Replacement Kit. The process includes removing the old injector, confirming all old internal components are removed, assembling the new injector components in the correct order, lightly greasing the new sealing components, and reinstalling the replacement injector onto the pump manifold.
Key Takeaways
- Clean dirt, debris, and build-up away from the chemical injector area before removing the old injector.
- Remove all old injector components, including the steel ball and spring.
- Check that the old spring is intact and that no broken pieces are left behind in the injector port or manifold.
- Apply a small amount of grease to the new O-ring and sealing components during assembly.
- We highly recommend looking up the torque specification for your specific pump and tightening the injector to the proper torque spec when available.
Pump and Chemical Injector Kit Used in the Video
The pump shown in this installation is an AAA 8.7GA12 triplex plunger pump. The chemical injector mounts into the pump manifold and includes small internal check-valve components that must be removed and reinstalled correctly.
The chemical injector kit shown in the video is the AAA Pump Chemical Injector Replacement Kit (7104228).
This kit includes:
- 1 barbed nipple with O-ring
- 1 stainless steel ball
- 1 spring
The injector uses a 1/8 “-28 BSPP (G) thread type with a 0.90 mm thread pitch.
When removing the old chemical injector, make sure all internal components come out with it, including the steel ball and spring. These pieces are easy to miss, but they are required for the chemical injector to seal and draw detergent properly.
Symptoms of a Chemical Injector That Needs Replacing
A chemical injector may need to be replaced if the pressure washer:
- no longer pulling soap through the chemical hose
- injector nipple is leaking
- internal parts are stuck, damaged, or missing
The injector uses small check-valve components to control the flow of chemicals. If the spring breaks or the ball does not sit correctly, water may come out of the chemical hose connection instead of the injector sealing the way it should.
Tools and Parts Used
For this installation, you will need the correct replacement chemical injector for your pump. Chemical injectors are not universal, so the thread type, fitting style, and pump model need to match. Please reference your manual to find the correct chemical injector before ordering or installing a replacement.
For the pump shown in the video, the replacement part used is the 7104228 AAA Chemical Injector Replacement Kit.
You may also need:
- 7104228 chemical injector kit
- Socket wrench that fits the injector body (in our case, 13mm socket)
- Clean rag
- (lithium-based) Grease for the ball, spring, and O-ring area
- Your pump model number or parts diagram for verification
Step 1: Shut the Pressure Washer Off and Release Pressure
Before removing the chemical injector, shut off the pressure washer first. Turn off the water supply, then release trapped pressure from the system by squeezing the spray gun trigger after the machine is off.
Once the pressure has been released, disconnect the water supply. Releasing pressure first helps prevent pressurized water from spraying out and makes the water supply easier to disconnect.
Make sure the pump and fittings are cool enough to handle before starting the repair.
Step 2: Locate the Chemical Injector
The chemical injector is installed on the pump manifold and features a small, barbed nipple for the chemical hose connection.
Remove the chemical hose from the injector nipple so the hose barb assembly can be accessed clearly.
Step 3: Remove the Old Chemical Injector
Use the correct wrench or socket to loosen the old chemical injector hose barb assembly from the AAA 8.7GA12 triplex plunger pump manifold. Turn it carefully so you do not damage the threads on the pump manifold or injector assembly.
Once removed, inspect the old injector. Look for corrosion, clogged chemical residue, worn O-rings, damaged threads, or broken internal parts.
Step 4: Remove All Internal Injector Components
After removing the chemical injector, check the manifold opening and the old injector body carefully. Make sure all components are removed, including the steel ball and spring.
These small parts control the injector’s check-valve function. If the old ball or spring is left inside the manifold, stuck in the hose barb, missing, or reinstalled in the wrong order, the new chemical injector may not work correctly.
The steel ball and spring should be accounted for before installing the replacement injector.
Step 5: Grease the Stainless-Steel Ball
Apply a small amount of grease to the stainless-steel ball from the 7104228 chemical injector kit.
The grease helps hold the ball in place during assembly and helps the ball seat correctly inside the hose barb.
Step 6: Install the Ball into the Hose Barb
Hold the barbed hose fitting upside down. Drop the greased stainless-steel ball into the hose barb so it sits on top of the small O-ring inside the fitting.
This placement is important because the ball is part of the injector’s internal check-valve assembly. If the ball is missing, installed incorrectly, or not seated properly, the injector may leak or fail to draw detergent.
Step 7: Grease and Install the Spring
Apply a small amount of grease to the top of the spring. Then push the spring down onto the ball inside the hose barb assembly.
The grease helps keep the spring in place during installation. This makes it easier to install the assembly back onto the manifold without the ball or spring falling out.
Do not pack the fitting with grease. Use just enough to help hold the parts in place while keeping the chemical passage clear.
Step 8: Install the Chemical Injector Assembly Back onto the Manifold
Carefully install the assembled hose barb, ball, and spring back onto the pump manifold. Keep the assembly positioned so the internal parts do not fall out during installation.
Start the fitting by hand first to help prevent cross-threading. Once the injector assembly is started correctly, tighten it carefully with the proper wrench or socket.
For final tightening, we recommend using a torque wrench when possible. For the 7104228 chemical injector installation shown here, torque the injector assembly to 110 in-lbs.
The 7104228 injector uses a 1/8 “-28 BSPP (G) thread type with a 0.90 mm thread pitch. Before installation, verify that this thread configuration matches the pump or parts diagram for your unit.
Do not overtighten the hose barb assembly. Small pump fittings and manifold threads can be damaged if the injector is forced or installed with the wrong thread type.
Step 9: Reconnect the Chemical Hose
After the injector is installed, reconnect the chemical hose to the injector nipple. Make sure the hose fits tightly and is not cracked, stretched, or loose.
If the hose is damaged or the detergent filter is clogged, the injector may still have trouble drawing soap even after the new injector is installed.
Step 10: Test for Soap Draw
After installation, test the pressure washer with the correct low-pressure soap nozzle or on the low-pressure setting. Chemical injectors usually do not draw soap in high-pressure mode.
Place the chemical hose and filter into the detergent container, run the pressure washer, and check that the soap is pulled through the hose.
If the machine still does not draw soap, check the soap nozzle, chemical hose, detergent filter, and injector connection before assuming the new injector is defective.
Common Mistakes to Avoid
These components are small and can be easy to miss:
- Avoid leaving the old steel ball or spring behind after removing the old injector
- Avoid installing the stainless-steel ball and spring in the wrong order
- Avoid using too much grease
- Avoid forcing the injector into the pump manifold
- Avoid overtightening the hose barb assembly
- Avoid testing soap drawing with a high-pressure nozzle
Final Check
Once the new chemical injector is installed, check for leaks around the hose barb assembly and injector nipple. Then confirm that the detergent is being pulled through the chemical hose during low-pressure operation.
If the injector is installed correctly and the rest of the soap system is clear, the pressure washer should draw detergent normally again.
Frequently Asked Questions
What chemical injector kit is used in the video?
The video uses the 7104228 AAA Pump Chemical Injector Replacement Kit. The kit includes 1 barbed nipple with O-ring, 1 stainless steel ball, and 1 spring.
What pump is shown in the chemical injector installation video?
The pump shown in the video is an AAA 8.7GA12 triplex plunger pump. Before ordering or installing a replacement injector, confirm your pump model number and parts diagram.
What thread type does the 7104228 chemical injector use?
The 7104228 chemical injector uses a 1/8 “-28 BSPP (G) thread type with a 0.90 mm thread pitch. Always verify the required thread type before installing a replacement injector.
Why do you put grease on the ball and spring during installation?
A small amount of grease helps hold the ball and spring in place while the hose barb assembly is installed back onto the manifold. This helps prevent the small internal components from falling out during assembly.
Where does the ball go inside the chemical injector?
The stainless-steel ball goes inside the upside-down hose barb and sits on top of the small O-ring inside the fitting. The spring is then pushed down onto the ball before the assembly is installed back onto the manifold.
Why is my pressure washer chemical injector leaking water?
Water can leak from the chemical injector nipple if the internal stainless-steel ball or spring is damaged, missing, stuck, or installed incorrectly. A worn injector or damaged O-ring can also cause leaking.
Why won’t my pressure washer draw soap after installing a new injector?
The pressure washer may not draw soap if it is being used with a high-pressure nozzle, if the chemical hose is clogged, if the detergent filter is blocked, or if the stainless-steel ball and spring inside the injector are not installed correctly.
Are pressure washer chemical injectors universal?
No. Chemical injectors vary by thread type, fitting style, flow range, and pump design. Always verify the correct replacement injector using the pump model number and parts diagram.
