Downstream Chemical Injector Buying Guide
A downstream injector adds detergent to the water after the pump, so harsh chemicals do not pass through the pump, unloader or heating coil. It works on the venturi principle: with a low-pressure soap nozzle on the wand it draws chemical; switch to a high-pressure tip and it stops so you can rinse.
Injector options at BCE
- High Draw Fixed (General Pump, ceramic ball, 4,500 PSI): 2-3, 3-5 or 5-8 GPM.
- High Draw Adjustable (4,500 PSI): 2-3, 3-5 or 5-8 GPM, adjustable chemical strength.
- High Draw Fixed Stainless Steel (5,500 PSI): 2-3, 3-5 or 5-8 GPM; also available with a 1/4 inch check valve installed (3-5 or 5-8 GPM).
- Fixed Dual Inlet (4,500 PSI): two 1/4 inch barbs, 2.1 or 2.3 mm orifice.
- Chemical filters: plastic (with or without check valve) or weighted stainless & brass with check valve, to keep debris out of the injector.
All injectors are 3/8 inch MNPT inlet/outlet, 1/4 inch hose barb, rated to 190°F, with a 20% chemical injection rate listed on the high-draw models.
- Match Your GPM: Injectors are strictly GPM-specific. An undersized injector chokes your flow, while an oversized injector will not create enough vacuum to draw chemical.
- Low-Pressure Drawing: Injectors only pull soap under low pressure when a soap nozzle is installed at the end of your wand. Switch back to high-pressure tips to automatically stop chemical flow and rinse.
- Troubleshooting Draw Loss: If your injector stops pulling detergent, inspect the internal ball, spring and check valve for chemical crust or debris before replacing the unit.
Pair with the right detergents, low-pressure soap nozzles, quick connect fittings and a cold water pressure washer or hot water pressure washer sized to your injector.
Frequently Asked Questions
What size chemical injector do I need?
Match the orifice to your pressure washer's flow: 1.8 mm for 2-3 GPM, 2.1 mm for 3-5 GPM, 2.3 mm for 5-8 GPM. An undersized injector restricts flow; an oversized one will not create enough vacuum to draw chemical.
Fixed or adjustable injector?
Adjustable injectors let you dial chemical strength at the valve. Fixed injectors are simpler and lower cost; many contractors use fixed injectors and control strength in the batch mix tank.
Standard or stainless steel injector?
The standard General Pump high-draw injectors use an acid-resistant ceramic ball and are rated to 4,500 PSI. The stainless steel versions are rated to 5,500 PSI. All are rated to 190°F.
Why is my injector not drawing soap?
A downstream injector only draws with a low-pressure soap nozzle on the wand; high-pressure tips stop the draw. If draw is lost, clean the ball and check valve of chemical crust and use a chemical filter on the pickup hose.
What fittings do the injectors use?
Inlet and outlet are 3/8 inch male NPT with a 1/4 inch hose barb for the chemical line. Add quick-connect fittings to install between the pump outlet and pressure hose.
