This is the page to read before buying anything in this hub. Three checks, and they take about five minutes. Skipping them is why so many surface cleaner listings carry reviews saying “barely turns” or “does not fit” — in almost every case the head was fine and the pairing was wrong.
Check 1: find your machine’s GPM
It is printed on the machine, usually on the same label as the PSI figure, written as something like 1.76 GPM or 1.2 GPM. Sometimes it is given as liters per minute, in which case divide by 3.785.
If no flow figure appears anywhere — which happens on budget machines, and is itself informative — assume 1.2 GPM or less and size accordingly. A machine proud of its flow states it.
Note the figure, not the PSI. Pressure is almost irrelevant to whether a surface cleaner spins. PSI vs GPM explains why.
Check 2: pick the matching head size
| Your GPM | Buy this size | Do not buy |
|---|
| Under 1.2 | A turbo nozzle instead | Any surface cleaner |
| 1.2 to 1.5 | 11 inches | 14 inches and up |
| 1.6 to 2.0 | 14 inches | 15 inches and up |
| 2.1 to 2.5 | 15 inches | 20 inches |
Worked examples from machines on this site. A Greenworks 1600 or Ryobi 1800 at 1.2 GPM: 11 inches. A Westinghouse ePX3500 at 1.76 GPM: 14 inches. A Westinghouse WPX3200 gas unit at 2.5 GPM: 15 inches. A Sun Joe SPX3000, which publishes no flow figure: treat as 1.2 and buy 11.
If you are between two sizes, take the smaller. An under-driven head cleans worse than a narrower one, and is also easier to steer.
Check 3: the fitting
Look at the end of your wand or gun where accessories attach. One of two things:
A square-shouldered push-on coupler with a sliding collar — that is 1/4-inch quick connect, and almost every surface cleaner fits it directly.
A threaded fitting — that is M22, and you need an adapter. M22 comes in 14mm and 15mm internal sizes which look identical; measure the inside diameter of the male thread’s center pin, or check your manual. A cheap adapter set covers it, and buying one at the same time as the head saves a wasted Saturday.
The two things that are not checks but matter
Your water supply. A machine can only deliver its rated flow if the tap can feed it. Time how long a 5-gallon bucket takes to fill from your outside tap: under 60 seconds is fine for any machine here. Much slower and your real flow is lower than your machine’s rating, so size down.
Hose length. A long run costs you a little pressure and flow. If you are borderline on size and running 50 feet of hose, size down.
Then buy
With your size settled, go to the main picks or, for a low-flow electric, the electric-specific page. If it arrives and still will not spin properly, the fix page works through the causes in order.
