What counts as low-volume pressure cleaning under the rules?

Start with what is missing. The district's definition gives no flow rate, no pressure and no named industry standard, and a reader looking for a number in it will not find one.

What it gives instead is a design test. Rule 40E-21.051(17) describes pressure cleaning by means of equipment “specifically designed to reduce the inflow volume as accepted by industry standards”. The test is about what the machine was built to do, take in less water, and it leaves the measure to industry standards it does not name. None of the documents quoted on this page names one either. The full wording, beside its neighboring definitions, is in the low-volume pressure cleaning glossary entry.

A volume of water moving through a machine is usually written as a flow rate in gallons per minute, and the definition could have set a ceiling in GPM. It does not. It sets no pressure ceiling either, so nothing in the rule text says a machine qualifies at one setting and fails at another.

The district's rule document for Chapter 40E-21 carries an effective date of 05/27/2012, and that is the wording quoted here.

The phrase does its work in two places, the district's shortage phases and the county's standing rule, and neither use fills the gap.

In the district's plan, each phase's other outside uses paragraph carries a pressure cleaning line. It restricts outside pressure cleaning to “only low volume pressure cleaning” on the days each phase's text lists. Those lines apply when a phase is declared, and the Board may order restrictions in lieu of or in addition to the phase text, so the order in force decides. The step from a warning to a declaration belongs to the answer on water shortage warnings and roof cleaning.

A neighboring line is easy to mistake for this one. In Phase I, mobile equipment washing must use low volume methods over a pervious surface, and the chapter's mobile equipment means vehicles, trailers and boats, so that line never reaches a building or a roof.

The county's summary of Ordinance 2015-27 names Low Volume Pressure Cleaning Equipment as one way to wash exterior home surfaces and roofs, and it uses that equipment name without defining it, and the ordinance itself is not quoted here, so this page does not say the county uses the district's definition. How the summary applies on a roof is covered with the Florida rules for a roof cleaning, and which local rule reaches a given address is sorted out in the water rules for Naples, Marco Island, Estero and Bonita Springs.

The only number in any of these documents is a pressure, and the district's test is about volume.

The City of Bonita Springs' Ordinance 21-07 summary answers that pressure washing is not restricted in the city, then adds a best-practice line to “use low-volume equipment that produces water pressure of 1,000 pounds per square inch to 4,000 pounds per square inch.” That range is the city's own conservation guidance. It is not the district's figure or the county's, and it describes how hard the water leaves the nozzle, not how much of it flows.

Pressure and volume are separate quantities. Pressure, written in pounds per square inch (psi), is the force of the stream; volume is how much water passes through the machine over time. A machine can push a small amount of water very hard. FDEP's guidance for vehicle and equipment washing pairs the two in exactly that way, recommending “high pressure, low volume washing techniques and equipment” to minimize wastewater.

That is also why the pressure arguments elsewhere on this site do not settle this one. Why soft washing names no pressure number is argued in why soft washing rests on a mechanism, not a number, and why roof cleaners keep pressure down is taken up in why roof cleaners use low pressure. Low pressure describes the stream; the district's test asks about inflow volume and the machine's design.

Whether a particular machine counts is not a question any published figure answers. During a declared shortage it goes to the South Florida Water Management District and to the water utility serving the address at the time.