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Foam cannon matching
Pressure Washer Foam Cannon: Orifice & Adapter Guide
Match a foam cannon to the pressure washer's flow, pressure, inlet connection and orifice requirement. Thick foam is not just a “more pressure” problem—restriction, water flow, chemical mix and the unloader all interact.
Two checks before shopping
Hydraulic match: GPM + PSI determine the approximate nozzle/orifice class. Mechanical match: the foam cannon plug/adapter must actually mate with the gun or wand.
The embedded aid uses MTM Hydro's currently documented orifice mappings as a reference, not as a universal standard for every foam-cannon brand.
Foam cannon orifice & compatibility aid
Enter the pressure washer's rated flow and working pressure. The tool calculates the standard nozzle number, then shows the nearest documented MTM foam-cannon orifice mapping.
MTM foam-cannon orifice mappings
| MTM orifice | Published nozzle number | Role in current MTM guidance |
|---|---|---|
| 1.1 mm | #3.0 | Included with current PF22; commonly considered for lower-flow requirements when #3.0 is the closer hydraulic match. |
| 1.25 mm | #3.5 | Factory-installed in current MTM foam cannons. |
| 1.5 mm | #5.0 | Larger-orifice option; MTM's own example says 3.5 GPM at 2000 PSI requires #5.0. |
| 1.7 mm | #6.5 | Additional larger-orifice option for machines whose nozzle requirement is closer to #6.5. |
Millimetre diameter and pressure-washer nozzle number are different measurements. Use the mapping published for the specific foam-cannon system.
Why 1.1 mm is not automatically the “electric pressure washer” orifice
Lower-flow electric machines often need a more restrictive orifice than higher-flow professional machines, but GPM alone is not enough. MTM tells users to size the foam-cannon orifice from the pressure washer's nozzle requirement, which depends on both GPM and PSI.
An orifice that is too small can create excessive back-pressure. MTM's troubleshooting guidance associates an undersized orifice with pulsation or machine cycling; a watery result can point in the other direction, but chemical selection and concentration also matter.
Connection compatibility: 1/4-inch QC, M22 and proprietary couplers
The current MTM PF22 with stainless plug includes a 1/4-inch quick-connect plug plus a 1/4-inch M22 adapter. That does not make every residential pressure washer plug-and-play. MTM notes that certain models from brands including Greenworks, Ryobi, AR Blue Clean, Generac and others use coupler geometry that can require a low-profile or model-specific fitting.
That is a model-level warning, not a claim that every machine from those brands is proprietary. Identify the actual gun/wand outlet and use the fittings guide before ordering adapters.
PF22 operating range is separate from orifice selection
MTM currently publishes the PF22 at 1100–5000 PSI, 1.4–5.3 GPM and 140°F maximum. Being inside that broad operating envelope does not mean the factory 1.25 mm (#3.5) or included 1.1 mm (#3.0) orifice is correct for every point in the range. MTM explicitly documents that higher-flow/lower-pressure combinations can need larger orifices.
Example from MTM: 3.5 GPM at 2000 PSI requires a #5.0 orifice, which MTM maps to 1.5 mm. The standard nozzle formula gives about #4.95, which is why the embedded aid returns that mapping.
Foam concentration vs. soap dilution
The amount of concentrate added to the bottle is not the same as the final chemical concentration hitting the surface. The foam cannon draws the bottle mixture into a much larger water stream, and the adjustment knob changes how much chemical is induced. Product viscosity, formulation, water hardness and the cannon's internal metering can also affect foam.
Follow the detergent manufacturer's instructions for safe dilution and surface compatibility. Do not treat a foam-cannon dial position as a calibrated final dilution ratio unless the manufacturer explicitly supplies that relationship.
Flow-sensing unloaders need special attention
MTM's current foam-cannon kit guidance warns that its foam cannons will not work correctly with flow-sensing unloaders and describes cycling/pulsation behavior. If you do not know your unloader type, treat it as an unresolved compatibility check rather than changing to a smaller orifice to force more foam.
After the orifice class and connection are identified
Compare foam cannons that support your machine's operating range and connection. If an adapter is required, verify the exact gun/wand interface separately.
Technical sources
- MTM Hydro — PF22 Foamer with stainless plug — current 1100–5000 PSI, 1.4–5.3 GPM and 140°F operating range; #3.5/1.25 mm installed and #3.0/1.1 mm included.
- MTM Hydro — 1.1 mm Foam Cannon Orifice — maps 1.1 mm to #3.0 and explains sizing by machine GPM/PSI.
- MTM Hydro — 1.25 mm Foam Cannon Orifice — maps 1.25 mm to #3.5 and identifies it as the standard installed MTM size.
- MTM Hydro — 1.5 mm Foam Cannon Orifice — maps 1.5 mm to #5.0.
- MTM Hydro — 1.7 mm Foam Cannon Orifice — maps 1.7 mm to #6.5.
- MTM Hydro — PF22 + Soap — connection caveats, larger-orifice example and flow-sensing-unloader warning.
Frequently asked questions
What foam cannon orifice size do I need?
Match the orifice number to your pressure washer's GPM and PSI using the standard nozzle relationship. MTM Hydro currently maps #3.0 to 1.1 mm, #3.5 to 1.25 mm, #5.0 to 1.5 mm and #6.5 to 1.7 mm for its foam-cannon orifices.
Is a 1.1 mm foam cannon orifice better for an electric pressure washer?
Not universally. A 1.1 mm MTM orifice corresponds to nozzle #3.0 and can be useful for some lower-flow machines, but the correct size depends on both GPM and PSI. An orifice that is too small can create excessive back-pressure and pulsation.
Can any foam cannon connect to any pressure washer?
No. Many professional-style foam cannons use a 1/4-inch quick-connect plug, but some residential pressure-washer couplers or proprietary systems require a different plug or adapter. Confirm the exact connection on the gun or wand.
Why does my pressure washer pulse with a foam cannon?
One documented cause is an orifice that is too restrictive, which can create excessive back-pressure and make the unloader cycle. MTM also warns that its foam cannons do not work correctly with flow-sensing unloaders. Check the exact manufacturer guidance before changing parts.
Does the foam cannon dial tell me the final soap dilution ratio?
No. The bottle mixture is only one part of the delivered concentration because the foam cannon also draws water through the pressure-washer stream. Follow the chemical manufacturer's dilution instructions and treat the cannon adjustment as a delivery setting, not a laboratory dilution measurement.