
Spot sensors catch water on the floor. Flow-based detection catches water that never reaches a sensor. Most commercial buildings need both, tied to a water balance.
Two kinds of leak
The first kind is visible damage: a burst pipe in a riser or a failed fitting above a ceiling. Spot sensors on the floor near risers, tanks and plant rooms raise an alarm when water reaches them.
The second kind is silent: toilets running, a stuck float valve on a cooling tower, an irrigation line broken underground. No sensor gets wet, but the meter keeps turning. EPA's leak table puts a toilet leaking 0.5 gallons per minute at 21,600 gallons a month, about $2,100 a year.
EPA WaterSense estimates leaks can account for more than 6 percent of a facility's water use, and says that if more than 10 percent cannot be accounted for, the facility may have leaks.
Four ways to find a leak
| Method | What it finds | What it misses |
|---|---|---|
| Spot sensors. | Water pooling at a known point. | Leaks into drains, underground or inside walls. |
| Flow monitoring. | Continuous flow when the building should be quiet. | Which branch is leaking, unless sub-metered. |
| Water balance. | The gap between supply and the sum of branch readings. | Very small leaks below meter accuracy. |
| Acoustic sensors. | Noise from pressurized leaks on mains. | Low-pressure and gravity lines. |
What to require
| Requirement | Why it matters here | Ask the vendor |
|---|---|---|
| Alerts by line and hour. | Knowing a leak exists is less useful than knowing where. | Show an alert with the line and start time. |
| A cost on every alert. | Teams prioritize by money. | Can alerts show the cost per day at our tariff? |
| Sensor health. | A dead battery means no alarm. | How do you report offline or low-battery devices? |
Where this is going
Water costs are rising: US household water and sewer bills went up 5.1 percent in 2025. Metering mandates are spreading too, from US federal buildings, which had to be water metered by October 2022, to Singapore's requirement that large users meter key areas.
How to choose
- Map risk pointsPut spot sensors where damage would be costly.
- Meter the main and big branchesFlow tells you about leaks no sensor will see.
- Set night floorsAgree the expected minimum flow per line.
- Test the responseTrigger a test alert and time the response.
Where Aqueduct fits
aQ WaterGuard uses flow and spot sensing together. Branch meters feed a live water balance, so unaccounted flow is located to a line and an hour, and the device health tab shows battery and connection rate for every sensor. Shut-off valves on relays can close a line where control is enabled, with owner approval.
Sources
| Source | Link |
|---|---|
| US EPA, WaterSense at Work, Section 2.3 Leak Detection | epa.gov |
| US EPA WaterSense, Getting Started | epa.gov |
| Bluefield Research via Water Online, 2026 | wateronline.com |
| US DOE FEMP, Water Metering Resources | energy.gov |
| Singapore PUB, Mandatory Water Efficiency Requirements | pub.gov.sg |


