Calculator
Surface cleaner size by GPM
Surface cleaner size depends mostly on flow (GPM). Sources disagree about small homeowner machines, so this page shows each one side by side instead of picking one.
What the sources say
| Source | Guidance | Type |
|---|---|---|
| Alkota surface-cleaner guide | Smaller machines (2–3 GPM) are often not big enough for a surface cleaner; 12–20 in for a 4 GPM machine; 24–30 in for 5–8 GPM. | Equipment manufacturer |
| Pittsburgh Spray Equipment | About 3 GPM minimum to run a surface cleaner; more GPM allows a larger cleaner. | Distributor |
| PressureWashingResource forum thread | Rule of thumb quoted by users: about 4 in of cleaner width per 1 GPM. | Forum rule of thumb |
The sources agree that more flow supports a larger cleaner. They differ for 2–3 GPM machines: the rule of thumb suggests roughly 8–12 in, while the manufacturer guidance says machines that small are often not big enough at all. Expect slow, overlapping passes with a small machine.
Nozzles on the spray bar
The bar’s tips share your machine’s flow, so divide the machine’s nozzle number by the number of tips (J. Racenstein nozzle guidance). The calculator above does this and rounds to the Cat Pumps nozzle selection chart sizes.
Sources checked 1 November 2026. This page does not claim hands-on testing.