GPM

The US EPA's WaterSense program spells out the unit in a sentence about showerheads, not washing equipment: “Did you know that standard showerheads use 2.5 gallons of water per minute (gpm)?” The expansion is the useful part; the 2.5 figure belongs to a showerhead and is not a washing number.

The one washing flow rate in the documents read for this page comes from paver cleaning. The Interlocking Concrete Pavement Institute describes a high pressure sprayer applying cleaner and water “at a rate between 2 and 6 gallons/minute (7.6 and 22.7 liters/minute),” in the same sentence as its 1,000 to 4,000 psi: one number for force and one for flow. The force half is defined at PSI, and what that sprayer is used to take off concrete pavers is on the paver cleaning page under what a paver cleaning removes.

ICPI's own sentence treats the flow rate as something adjusted on the job, not a fixed setting: “The rate of flow is adjusted to ensure sufficient rinsing.” The 2 to 6 gallons per minute range is the window that adjustment sits inside, not a single number to hit.

Florida's water rules lean on volume rather than pressure for a related term. The South Florida Water Management District defines low-volume pressure cleaning as pressure cleaning by equipment “specifically designed to reduce the inflow volume as accepted by industry standards,” with no gallons per minute figure in the definition. The term itself is defined at low-volume pressure cleaning, and what qualifies under the rules is answered at what counts as low-volume pressure cleaning.

No association or roofing maker document read for this page publishes a gallons per minute figure for a roof wash of any kind, soft wash or pressure wash. EPA's 2.5 gpm is a showerhead figure, and ICPI's 2 to 6 gallons per minute is a paver figure; carrying either one onto a roof, or treating a soft wash as measurably lower in flow than a pressure washer, is not a claim any source read here supports.

The washing rules that touch a Naples roof or paver driveway name a class of equipment rather than a gallons figure, and how those rules sit across the year is set out in the water calendar.