Shared Water Meter, Hidden Leak, and a Short Performance Window
A 90,000 ft² four-building office campus on 3 acres uses municipal water for domestic fixtures, cooling tower makeup, and irrigation. The campus has one master water meter; only two of four buildings have sub-meters, and irrigation has no dedicated meter. A fixture retrofit five years ago replaced toilets and aerators, but a recent walkthrough found several continuously running toilets and an irrigation valve leaking at night. The water bill shows annual consumption of 6.2 million gallons, with a 12% increase over the previous year. The team is preparing LEED O+M v4.1 recertification and wants to pursue water efficiency credits. The utility provides monthly bills but no hourly data; a third-party leak detection vendor offers a one-time acoustic survey. The owner wants to avoid installing new meters before the performance period ends.
1. How should the team establish reliable water performance and prerequisite compliance with only one master meter?
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The master meter can support building-level water performance if it covers all potable water uses and monthly bills are complete for a consecutive 12-month period. The team should reconcile the 6.2 million gallons against fixture, cooling tower, and irrigation estimates to understand the unexplained increase. Because the master meter does not separate irrigation or cooling tower makeup, the project cannot confidently attribute savings or leaks without submetering or a documented engineering calculation. For prerequisite compliance, confirm that the master meter is permanent and records total building water use. For credit calculations, use the same 12-month period and document any excluded uses only if the rating system allows them. The one-time acoustic survey is useful for locating leaks, but it is not a substitute for metering; it should trigger repair and a follow-up verification read.
2. What metering and submetering would you recommend, and why?
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I would keep the master meter as the building-level meter and add dedicated submeters for irrigation and cooling tower makeup as soon as practicable. Irrigation is a major seasonal use and is the most likely source of the nighttime loss; cooling tower makeup can reveal drift, overflow, or excessive cycles of concentration. Submetering the two buildings without meters would improve leak isolation and tenant engagement, but it is less urgent than separating irrigation and tower use. The owner’s desire to avoid new meters before the period ends is understandable, but installing them after the period would still help future recertification and water management. The team should not claim precise irrigation savings without measurement. A reasonable sequence is: repair known leaks, install dedicated irrigation and tower meters, verify with master-meter reads, and then define the performance period after stabilization.
3. How should the leak and the 12% consumption increase be handled in the performance period?
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Do not cherry-pick a low-consumption month or exclude the leak without disclosure. First repair the running toilets and irrigation valve, then take consecutive master-meter readings to confirm the fix. If the leak occurred during the proposed performance period, the period may still be used if it represents actual operations, but the application should document the event and any corrective action. If the project wants to demonstrate efficiency, it may be better to start the performance period after repairs and stabilization, provided the timing still fits the recertification window. The acoustic survey can support the narrative but should not replace meter data. The 12% increase should be investigated rather than averaged away: compare seasonal irrigation, tower makeup, and fixture use. A transparent explanation is more defensible than a performance period that hides an operational failure.