Foam cannons, soap, and the bleach rule.

Three ways soap actually gets on a surface

1. Soap tank / downstream injector. The pump only sees water. Detergent sips in after the pump, at low pressure. This is the safe default on most consumer machines.
2. Foam cannon on the wand. 1/4″ QC bottle, air mixer, thick cling. Works best at roughly 2+ GPM and 1,500+ PSI. Great for vehicles and degreasing concrete before a rinse.
3. Pump sprayer or X-jet. The right tool for SH house wash. Keep oxidizers off the pump circuit entirely.

What can go in a foam cannon

• Pressure-washer-rated vehicle soap or house wash labeled pump-safe / downstream-safe.
• Concrete degreaser that says it is safe for foam cannons — still keep solvents off the inlet.
• Follow the bottle. Most cannons want 1–3 oz of concentrate, then the venturi dilutes again.

Dish soap as a one-off rinse is a bad habit: surplus surfactants dry seals. Dedicated soaps are cheap compared to a pump.

How to foam without making a mess

• Work in the shade. Dried soap on hot concrete or paint is a streak machine.
• Apply with a 40° white tip or the cannon’s own orifice, bottom to top on vertical work.
• Dwell a few minutes. Do not let it bake.
• Rinse with the correctly sized 25° or 40° tip — see the orifice chart.
• Flush the cannon with clean water when you are done. Bleach residue in a cannon still is not “through the pump,” but it will wreck the cannon’s internals.

House wash is a different kit

Soft washing organic staining on siding is SH + surfactant + lots of rinse water, applied downstream. That is not a foam-cannon-on-the-gun job. If you want that stack, start with an injector and keep the pump on fresh water only.

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