Water Finance and Management reported that Mueller Water Products, Inc. has entered into an agreement to transition its metering business subsidiary, Mueller Systems, to ZENNER USA, which is part of the Minol-ZENNER Group. The Water Finance and Management report on the Mueller transition covers the corporate transaction. It does not describe what happens to installed meters in the field, so a utility that buys, maintains, or tests Mueller-supplied meters should work those details out on its own schedule.
Accuracy drifts where the flow is small
A water meter's accuracy is not a fixed property of the device. Mechanical registers wear, bearings and measuring chambers change clearance, and the resulting error is not spread evenly across flow rates. Low-flow registration usually shows the problem first, because slow continuous draws and intermittent refills sit near the bottom of a meter's sensitive range. A meter that under-registers at those rates can look normal on a monthly bill, while the gap appears as non-revenue water in the utility's balance.
The mechanism varies by design. Positive displacement, multi-jet, turbine, electromagnetic, and ultrasonic meters respond differently to wear, air entrainment, and debris, so a mixed fleet cannot be tested under a single assumption. Size matters as well. A large compound meter serving a commercial account carries different error risk than a residential 5/8-inch unit, and the test program should be stratified accordingly.
What the test record has to hold
A test record is useful only if someone can reconstruct the conditions under which each meter was checked. At minimum, each entry should carry the serial number, manufacturer and model, size, install date, and the date and results of every prior test. It should record the flow rates tested, including low, transitional, and high points, with as-found and as-left error at each. It should name the procedure followed, the test bench or field tester used, the calibration date of that equipment, and the person or contractor who performed the work.
Sampling is the practical compromise for most utilities. A sample describes the population only if it was drawn to represent that population, which means random or stratified selection by size, age, and location rather than the meters that were easiest to pull. Results from a convenient sample tend to describe the convenient meters. Record the sampling method alongside the results so a later reviewer can judge what the numbers cover.
Why a supplier change touches the file
A corporate transfer does not by itself change the accuracy of an installed meter. It can change the people and systems a utility relies on to answer questions about that meter. Test history often sits in a vendor portal, a data platform, or a service agreement. Replacement registers, calibration support, and parts availability depend on whichever company stands behind the product. The announcement does not address any of these, so they are questions to put to the supplier in writing, with dates, before a routine order or replacement cycle depends on the answers.
A sequence before the change
Start with an inventory that groups meters by size, model, and install period, and flag any group without legible test history. Pull the most recent field results for each group and check whether low-flow points were included. Compare consumption trends on large meters against production and sales records, and treat any gap as a lead for testing rather than a finding. Decide in advance whether testing will precede or follow any register, firmware, or communication module changes, because a change made mid-test can make before and after results hard to compare.
The tradeoffs are real. Full-fleet testing gives the clearest answer but consumes crew time and may pull meters that are performing well. Sampling is cheaper but can miss a failing subgroup. Replacement on an age schedule is administratively simple, though it can remove accurate meters while leaving drifting ones in service if the schedule does not match the wear pattern. The right mix depends on the utility's non-revenue water history, its billing exposure on large accounts, and the records it already holds.
What to write down
Whatever the utility decides, the decision belongs in the file. Record the inventory date, the sampling design, the calibration history of test equipment, the results by flow point, and the date of each supplier statement relied upon. A meter fleet is a set of measurements that will be questioned later, usually by an auditor, a rate case reviewer, or a successor who did not see the original work. The file should answer those questions without relying on anyone's memory.