Troubleshooting Guide: Suttner ST-160 Single Foam Injector

The Suttner ST-160 is a durable, high-efficiency downstream chemical injector used in countless professional wash setups. It’s designed to draw soap or degreaser into the water stream when used with the proper nozzle and pressure differential. If your injector isn’t drawing chemical, pulling consistently, or foaming properly, this guide will walk you through the most common issues and their solutions.

1. Injector Not Drawing Chemical

Likely Causes & Fixes:

Soap nozzle or foamer not low-pressure enough
✅ Use a QC soap nozzle or downstream foamer like the Chrome Cannon 2.0 with an enlarged orifice (e.g., 4.0+).
❌ High-pressure nozzles (rinse or turbo tips) will not allow chemical draw.
Pickup tube is disconnected, kinked, or blocked
✅ Ensure the clear pickup hose is securely attached to the injector barb.
✅ Check for kinks or internal clogs in the hose or strainer filter.
Check valve inside injector is stuck closed
✅ Soak the injector body in warm water or a vinegar solution to dissolve hardened soap residue.
✅ Rebuild kits are available to replace internal spring, ball, and seals if necessary.
Injector installed backwards
✅ Confirm the flow direction using the arrow on the brass body. The arrow must point toward your gun or foamer, not the pump.
Too much backpressure from accessories
✅ Ensure your foamer has a large enough orifice to drop pressure and activate the venturi.
✅ Try testing with a known working soap nozzle to confirm injector function.

2. Injector Drawing Intermittently or Inconsistently

Likely Causes & Fixes:

Air leak in pickup line
✅ Check the pickup hose and all fittings for cracks, loose barbs, or missing clamps. Air leaks will break suction and stop draw.
Excessive lift height or long pickup tube
✅ Keep the chemical container within 3–4 feet vertically of the injector and avoid long hose runs.
Fluctuating inlet pressure
✅ Inconsistent pump output or GPM will disrupt the injector’s venturi effect.
✅ Test with a consistent flow source and verify machine performance.
Viscous chemical or clogged metering adjustment
✅ High-viscosity products may need to be pre-diluted or drawn through a wider pickup tube.
✅ Back out the metering screw and clean it if flow is restricted.

3. Foaming Is Too Weak or Chemical Ratio Seems Too Lean

Likely Causes & Fixes:

Metering screw set too low
✅ Turn the adjustment knob counterclockwise to increase chemical draw.
Orifice in foamer too small
✅ Make sure you're using a foamer or nozzle with the correct orifice size (e.g., 4.0+). A small orifice creates too much backpressure.
Soap too diluted
✅ Start with a stronger mix in your chemical container (e.g., 1:1 or 2:1) and adjust as needed.
Foamer or cannon is clogged or restricted
✅ Clean the mesh filter and nozzle tip in your foamer cannon.

4. Injector Leaking at Fittings or Barb

Likely Causes & Fixes:

Worn or damaged O-rings or thread sealant
✅ Apply Teflon tape or thread sealant paste to all threaded connections.
✅ Replace any cracked or flattened O-rings or seals.
Loose fittings or overtightening
✅ Make sure all fittings are snug but not over-torqued to avoid cracking brass threads.

Maintenance Tips

✅ Flush with clean water after each use—especially when using high-pH or caustic chemicals.
✅ Inspect the check valve regularly (spring + ball assembly) for debris or corrosion.
✅ Replace the pickup line and strainer every few months or as needed.
✅ Keep the injector dry when not in use to extend internal component life.

When to Rebuild or Replace the Injector

Your ST-160 can last years with regular maintenance, but over time, internal wear can reduce draw performance. Consider rebuilding or replacing if:

Chemical draw has dropped significantly
Cleaning and flushing doesn’t restore function
Internal corrosion or cracking is visible
You’ve used harsh acids or chemicals not rated for brass/stainless

Rebuild kits are available from Chem-X or authorized dealers and typically include the spring, ball, O-rings, and seals.

Still Need Help?

If you’ve run through this guide and still aren’t getting performance out of your ST-160, contact our support team with the following:

Your pressure washer specs (PSI and GPM)
What type of soap or chemical you're using
The nozzle or foamer setup at the end of your line

We’ll help you troubleshoot your specific setup and get your system running at full strength.