Last reviewed and updated: 2026-09-24
Commercial and multi-family leak detection differs from residential work in three ways: the systems are larger and shared, the property cannot simply be shut down for testing, and a single inflated bill is often several leaks rather than one. The approach is a water loss audit, submeter and zone analysis to quantify and localise the loss, then targeted detection within the identified zone, scheduled around occupancy and trading hours.
On a multi-unit or commercial property an unexplained bill is rarely one leak, so the approach is a submetered audit. The underlying methods are the same as residential slab and service line work.
Where commercial water loss hides
- Irrigation across common areas: large zones running overnight on timers
- Continuously running toilets and flush valves across many units or restrooms
- Cooling tower and make-up water systems with faulty float controls
- Buried mains between buildings on a shared campus
- Pool, water feature and fountain systems with auto-fill masking the loss
- Failed backflow preventers and pressure-reducing valves
- Unit-level leaks under slabs in older apartment and condominium stock
The water loss audit approach
- Establish the baseline. Compare billing history against occupancy and seasonal patterns to quantify how much loss is genuinely unaccounted for.
- Read the meters at low demand. Overnight readings on a property that should be static reveal continuous flow.
- Isolate by zone. Building by building, wing by wing, irrigation separately, closing valves in sequence to narrow where the loss sits.
- Survey the identified zone. Acoustic survey of buried mains, thermal scanning of accessible runs, camera inspection of drains.
- Check fixtures at scale. In multi-family, a proportion of units will have running toilets at any time, and the aggregate is substantial.
- Report and prioritize. Document each loss found with its location, estimated volume and recommended remedy so the work can be scheduled and budgeted.
HOAs and apartment communities
Shared-meter properties have a particular problem: nobody owns the leak. The community pays for water lost in individual units, and individual residents have no visibility or incentive to report a running toilet. A periodic water loss audit is usually the only way that gets caught, and on a large community the recovered volume typically pays for the audit several times over.
Cobb County's leak adjustment program applies to the account holder, which on a shared meter is the association rather than the resident, another reason to document every leak found and repaired.
Working around the business
Retail, restaurant and office properties cannot lose trading hours to a diagnostic. Detection is scheduled around that, overnight or before opening for acoustic work, which also happens to be when background noise is lowest and acoustic detection works best.
Frequently asked questions
How is commercial leak detection different from residential?
The systems are larger and often shared, the property cannot simply be shut down for testing, and an inflated bill is frequently several separate leaks rather than one. The work starts with a water loss audit to quantify and localise the loss by zone before detection begins.
What is a water loss audit?
A structured process of comparing billing history against expected usage, taking meter readings at low-demand periods, and isolating the property zone by zone to establish where unaccounted water is going. It produces a documented list of losses with locations, estimated volumes and recommended remedies.
Our HOA water bill keeps rising. Where do we start?
With overnight meter readings while the community should be static, then zone isolation across buildings and irrigation. On shared-meter communities a proportion of units will have running toilets at any given time, and the aggregate volume is usually the largest single item.
Can detection be done without closing the business?
Yes, and it is normally scheduled that way. Acoustic work is often done overnight or before opening, which also produces better results because background noise is at its lowest.
Who claims the leak credit on a shared meter?
The account holder, which on a shared-meter community is the association rather than the individual resident. That is another reason to document every leak found and repaired, the paperwork supports the account holder's claim.
How often should a large property be audited?
Annually is a common cadence for multi-family and campus properties, with an immediate audit any time billing rises without an explanation in occupancy or season.