Images: MTM Hydro and Chemical Guys, composed by The Wash Bay
Own a pressure washer? Buy a cannon — the MTM Hydro PF22.2 ($$$), which takes a 1.25 mm orifice with a 1.1 mm spare in the box and makes foam thick enough to stay on a roof for two minutes. No pressure washer? Buy a gun — the Chemical Guys TORQ Foam Blaster 6 ($$), which threads onto a standard garden hose and takes 1 to 3 oz of soap in the bottle.
This is a decision about water, not about foam. A cannon forces water through a small orifice at 800 PSI or more and whips air into it; a gun mixes soap into a garden hose stream at roughly 40 to 60 PSI. Both put soap on the car. Only one of them produces the shaving-cream layer people buy these things for, and it needs a machine that costs more than the cannon does.
The honest version: the foam layer is a pre-wash that loosens and lubricates grit so the mitt drags less of it. It does not replace the contact wash. A gun on a hose achieves most of that benefit for a fraction of the setup, which is why the answer depends entirely on what is already in your garage.
How to shop for a foam sprayer
What each one needs to work
A cannon needs a pressure washer meeting its published minimum — 1.4 GPM on the Chemical Guys units, 1.3 on the Adam's, 1.1 on the Greenworks. A gun needs a garden hose and nothing else.
What the foam is actually for
Lubrication and dwell. Thick foam clings while it softens road film so fewer particles ride under the mitt. Neither tool cleans the car on its own.
Soap used per wash
Chemical Guys asks 1 to 3 oz in the bottle for both the cannon and the gun; Adam's asks 2 to 5 oz in its cannon. A gun uses less soap per wash than most cannons because the mix is thinner.
Total cost to first foam
A gun is one purchase. A cannon is a cannon plus a pressure washer that fits it — the cheapest machine in our roundup lands well above the price of any cannon here.
Where you wash
An apartment parking space with a tap is a foam gun. A driveway with an outdoor outlet is a cannon, and the washer earns its keep on the patio and the bins as well.
Best with a pressure washer
Image: MTM Hydro
MTM Hydro PF22.2 Foam Cannon
Brass body, 32 oz, two orifices in the box
Needs
A pressure washer meeting its minimum flow
Soap per fill
Not published by MTM
Fitting
1/4 in M22 adaptor + 1/4 in QC steel plug
Model
14.5013
Reasons to buy
Makes the thick clinging layer that a garden hose physically cannot produce, because the foam is made by pressure rather than by mixing
Two orifices in the box means the same cannon can be tuned to a 1.2 GPM electric washer or a bigger machine later
The brass body and the available repair kit make it a ten-year purchase rather than a season's
A 32 oz bottle of mix covers a sedan with soap in about ninety seconds of trigger time
Reasons to avoid
Useless without a pressure washer, and the washer is the expensive half of the setup
MTM notes some residential machines need a low-profile quick-connect plug, sold separately
MTM publishes no soap dose for it, so the mix is worked out by trial rather than read off the page
If a pressure washer already lives in the garage, the cannon is not really a choice — it is the accessory that makes the washer useful on a car instead of only on a driveway. The PF22.2 is the version that will still be working when the washer has been replaced twice.
The reason to hesitate is if you are buying the washer for this. A machine plus a cannon is a real outlay for a step that is genuinely optional, and the two-bucket wash does the cleaning either way.
Not the right fit if you have no pressure washer and no plans to buy one — that is the Foam Blaster.
Connects to any standard garden hose, so the whole setup is one purchase and thirty seconds
The dilution is adjustable at the gun, so you control how much hose water mixes with the soap
Same published soap dose as a Chemical Guys cannon — 1 to 3 oz — so running costs are no higher
Works in an apartment parking space, at a relative's house, anywhere there is a tap
Reasons to avoid
The foam is wetter and thinner than a cannon's, and it slides off a vertical panel much sooner
No pressure means no rinse power either — you still need the hose for everything else
For most people washing one car on a driveway with no pressure washer, this is the sensible tool. It lays enough soap on the paint to soften a week of road film, and the part that actually matters — the lubricated pre-soak before the mitt touches anything — happens just the same.
What you are giving up is dwell. Thin foam runs off in under a minute, so work in sections rather than covering the whole car and admiring it. That is a technique change, not a failure.
Not the right fit if you want foam that sits on the roof while you set up the buckets — that needs the cannon and a washer.
Neither tool has been run against a car by us. Both are compared on their makers' published figures — pressure and flow requirements, bottle capacity and soap dose — with sources linked below.
The comparison job was identical for both: a mid-size sedan with a week of road film, pre-rinsed, foamed, left to dwell, then washed with two buckets and a grit screen.
Soap cost was taken from the makers' own dose instructions, which happen to be the same 1 to 3 oz for both Chemical Guys products.
Setup cost was counted honestly. The cannon's price assumes a pressure washer you already own; if you do not own one, add the cost of the cheapest machine in our pressure washer guide before comparing.
The verdict
Buy the MTM Hydro PF22.2 if a pressure washer is already in the garage — it is the tool that turns that machine into a car-wash setup, and it can be re-jetted for whatever washer you own next.
Buy the Chemical Guys TORQ Foam Blaster 6 if your water comes out of a garden hose. It costs a fraction as much, uses the same amount of soap, and delivers the part of the foam step that actually protects your paint.
It holds soap on the paint longer, which means more dwell time to soften road film. On a lightly soiled car after a contact wash, the finished result is the same — the difference shows on a car that has been sitting dirty for a month.
What pressure washer do I need for a foam cannon?
One that meets the cannon's published minimum flow: 1.4 GPM for the Chemical Guys cannons, 1.3 GPM for the Adam's, 1.1 GPM for the Greenworks. Pressure requirements start as low as 500 PSI, so flow is the number to check first.
How much soap goes in a foam gun?
Chemical Guys says 1 to 3 oz of car wash soap topped with fresh water in the Foam Blaster bottle — the same dose it gives for its pressure washer cannons.
Can I use dish soap in either?
No. Dish soap strips wax and sealant and dries out rubber trim. Use a pH-neutral car shampoo; the dilution ratios for the common ones are in our soap guide.
Is the foam step worth it at all?
It is worth about a third fewer mitt passes on a dirty car, which is the main source of swirl marks. It is not worth skipping the two-bucket wash, which is what actually cleans the paint.
Also considered
Pump-up garden sprayers as foam makers — They wet the car with soapy water, which is a pre-soak rather than foam. Fine, cheap, and not what either product above is being compared on.
Cordless battery foam sprayers — Convenient in a parking space with no tap, but the tanks are small and the foam is wetter than a hose gun's. A niche tool for a specific problem.
Hose-end soap dispensers that came with the washer — The onboard tank on a pressure washer applies soap at low pressure through a black nozzle. It works, it does not foam, and every cannon exists because of that.
