Can entrained air affect commercial water meter readings?

What “entrained air” means

Entrained air is free gas moving with the water as bubbles, pockets, or a larger air volume. It is different from gas that is fully dissolved in water. When both free air and water cross a meter, the meter is seeing two-phase flow rather than the single-phase water condition for which water meters are normally selected and tested.

Why meter technology changes the answer

“Commercial water meter” describes several measurement methods, not one mechanism. The U.S. EPA and AWWA both emphasize choosing the proper meter type and size for the actual consumption pattern and maintaining its accuracy over time.

These are diagnostic considerations, not a prediction for a particular meter. The make, model, size, orientation, installation requirements, and utility test history matter.

What the research does—and does not—establish

A peer-reviewed laboratory study published in Water Resources Management reproduced an intermittent-supply event: an empty service pipe was pressurized and refilled through a mechanical meter. In those test conditions, the meter registered air before the water front arrived, producing over-reading. The researchers also found that air-valve location affected the measured air volume and pressure response.

That is credible evidence for a specific phenomenon, not proof that all commercial meters routinely add the same amount to a bill. The experiment modeled pipe filling after supply interruption. A continuously pressurized building, a different meter technology, or dispersed microbubbles may behave differently. Manufacturer instructions reinforce this variability: for example, Neptune states that retained air can affect its C&I ultrasonic meter’s accuracy, while an empty pipe prevents that model from registering consumption.

Questions commercial property teams ask

Can air cause a commercial water meter to read high?

It can under specific two-phase-flow conditions. Controlled research has documented over-registration when air crosses some mechanical meters during pipe refill, but the result depends on meter technology, pressure, installation, and the amount and form of free air. A high bill by itself does not establish the cause.

Does every water meter count entrained air the same way?

No. Positive-displacement, turbine, compound, ultrasonic, and electromagnetic meters use different measurement principles. Free air can produce over-reading, under-reading, uncertainty, or an empty-pipe condition depending on the meter and operating circumstances.

How should a property test whether entrained air affects billing?

Start with bills and interval data, confirm rates and meter multipliers, identify the installed meter, and document outages, pressure changes, and pipe-refill events. Then coordinate an authorized accuracy test or controlled comparison with the utility, a licensed plumber, or a qualified meter professional.

Why a commercial water bill may be high

Air is one hypothesis in a broader investigation. Start with the explanations that can be checked directly:

1. Billing inputs: confirm the service dates, rate changes, meter multiplier, sewer calculation, and whether the read was actual or estimated.
2. Leaks and continuous use: review overnight or closed-hours demand. EPA WaterSense recommends using frequent meter data to identify leaks.
3. Operating changes: account for occupancy, irrigation, cooling, laundry, kitchens, cleaning, production, and seasonal demand.
4. Meter fit and condition: identify the meter type, size, age, installation orientation, maintenance history, and low-flow performance.
5. Air-producing events: document outages, repairs, pressure swings, pump cycling, drained sections, and recurring pipe refill events.

A defensible site investigation

A useful investigation connects the utility bill to physical evidence at the meter. It should be coordinated with the utility, a licensed plumber, or a qualified meter professional; do not modify utility-owned equipment without authorization.