How do water leak detection methods compare?
Ask ten people what water leak detection means and you get two answers. One group means finding a leak that is already causing a problem. The other means knowing the moment a new one begins. Comparison articles are confusing because they mix the two.
The useful way to sort the methods is by where the equipment lives.
What are the on-site methods?
Equipment that arrives with a technician, does a job, and leaves. Priced per visit.
Acoustic detection and correlation. Listening equipment picks up the sound a pressurized leak makes as water escapes. Ground microphones work on buried pipes. Correlators use two sensors and the time difference between them to calculate a position, often within a few feet under good conditions.
- Good at: pressurized metal pipe, buried lines, pinpointing before you dig.
- Poor at: plastic pipe, which carries sound badly; unpressurized drains; noisy mechanical rooms.
Thermal imaging. An infrared camera shows temperature differences through building materials. A hot water leak behind a wall reads as a warm patch.
- Good at: hot water lines, radiant floors, finding the wet area without opening a wall.
- Poor at: proving what it found. It shows temperature, not water, so a thermal bridge or a duct reads as a signal too.
Tracer gas. The line is drained and charged with a 5% hydrogen, 95% nitrogen mix, which is non-flammable at that concentration, then escapes through the leak and is picked up at the surface.
- Good at: the hard ones. Plastic pipe, low pressure, and leaks acoustic methods cannot hear.
- Poor at: convenience. The system comes out of service to do it.
Moisture meters and probes. Cheap, quick, and the standard way to map how far water has already traveled. They find where water ended up, not where it came from.
What are the always-on methods?
Equipment that stays in the building and reports continuously. Bought once, with a platform subscription.
Flow sensing. A sensor on the main line reads flow minute by minute and learns what normal looks like for that building. This is the most versatile of the three, and the one most comparison articles get wrong, because it does three separate jobs:
- It finds leaks you already have. A base flow that never returns to zero overnight is the signature of a continuous leak, and it shows up in the data on day one, before anyone has reported anything.
- It catches new ones as they start, including at 2 a.m. on a Saturday.
- It helps you work out where. Flow rate tells you roughly how big. Time-of-day pattern tells you what kind: an overnight constant is a fixture or a buried line, a mid-morning spike is use, a fixed daily block is irrigation. On a submetered building, isolating zones narrows it further. That is diagnostic work, done from data, before anyone walks the site.
Point leak sensors, also called point-of-leak sensors. Small sensors placed where water first appears: mechanical rooms, under water heaters, beside laundry stacks. They detect water on contact and alert immediately. Cheap, and they answer in seconds the question an on-site survey takes an afternoon to answer, because the sensor is already in the room. The other family is rope or cable sensors, which trade precision for coverage along a run.
Automatic shut-off valves. Not detection, but the reason detection pays. A motorized valve closes on a major leak without waiting for a human.
Temperature and humidity sensing. The preventive layer. A cold snap in an unheated space is a burst pipe you have not had yet.
Does flow data really help locate a leak?
Yes, and there is a documented case. An apartment community in Mayfield, Ohio, managed by the multinational real estate investment firm Stoneweg, suspected it had a constant-flow problem. Flow sensing confirmed a pre-existing leak and gave the team flow rate and time-of-day patterns to work with. The result, over 2021-2022: a 31% reduction in water expenses year over year, a $72,000 refund for wasted water plus a sewer credit, 2.7 million gallons saved, and an 805% return. Read the full case study.
Nobody sent a correlator. The data narrowed it.
That does not make acoustic or tracer gas obsolete. For a buried service line, the final few feet still need someone on site with equipment. The difference is that flow data usually tells you a leak exists, roughly how big, and which run to look at, before you book anyone.
How do the methods compare?
The table below sorts the three families by what each one can actually do.
| On-site methods | Flow sensing | Point leak sensors | |
|---|---|---|---|
| Finds a leak you already have | Yes | Yes | Only if water reaches the sensor |
| Catches a new one as it starts | No | Yes | Yes |
| How precisely it locates | To within a few feet, on the pipe | Whole building from the main line, or by zone, riser, wing or unit wherever flow is measured | To the room the sensor sits in |
| Tells you what kind of leak it is | Only by inspection | Yes, from flow rate and time-of-day pattern | No |
| Finds waste that makes no mess | No | Yes | No |
| Present at 2 a.m. | No | Yes | Yes |
| Works on buried pipe | Yes | Detects and sizes it; the final few feet need a specialist | No |
| Cost shape | Per visit | Equipment plus subscription | Equipment plus subscription |
Swipe the table sideways to compare all three methods.
Read the flow sensing column as the reason it is usually the first thing a building installs. It is the only method that answers both questions.
Why does the distinction matter commercially?
Because 56% of floods happen after hours, per the 2026 State of Water Management Report, and roughly 1 in 4 monitored buildings had at least one flood event in 2025. A method that requires someone to arrive with equipment cannot catch a leak that starts on a Saturday night. It can only measure the damage on Monday.
The waste side makes the same point from the other direction. The report flagged 3.4 billion gallons of water waste in a single year, mostly running toilets, stuck irrigation, and slow leaks that never make a mess. No survey is ever booked for those, because nobody knows to book one.
How does Alert Labs fit?
Alert Labs builds the always-on side: flow sensors like the Flowie O water flow sensor, point leak sensors like the Floodie flood sensor & water leak detector, automatic shut-off with the Shuttie® automatic water shut-off valve, and the AlertAQ™ water intelligence platform that learns each building's normal water pattern and routes alerts by person and schedule. Sensors can arrive already named for their location, so the alert says which room.
Alert Labs does not sell leak-locating services. The alert, the location, and the follow-up are all part of the subscription.
Read what acoustic leak detection is, what a commercial water leak detection system is, water leak detection solutions, or what one costs.