Most multifamily water problems don't start with a burst pipe. They start with a toilet flapper that won't seal, a leaking boiler fill valve, or a slab leak nobody can see. Those leaks run around the clock and show up on the water bill weeks later. Some of them end as water damage. A good multifamily leak detection system catches them in days, not billing cycles, and points your maintenance team at the right building.
This guide covers how the main types of apartment leak detection work, what to ask any vendor, how the best-known systems differ, and how to estimate payback before you buy.
What multifamily leak detection actually has to catch
An apartment building has three kinds of water loss, and each calls for a different tool:
- Continuous hidden leaks. Running toilets, dripping fixtures, leaking water heaters and boilers, and slab or underground leaks. Each one is small. Together they add up across a building and can run for months.
- Sudden failures. Burst supply hoses, failed fittings, and broken pipes. These cause the fastest damage and need an alert within minutes.
- Water on the floor. Overflowing drain pans, a leaking dishwasher, a backed-up drain. The supply line may look normal, but water is reaching places it shouldn't.
The scale of the first category surprises most owners. In NOWi's Los Angeles apartment portfolio study, 72% of 47 buildings were leaking in the first week of data, about 794,000 gallons a month, or about $190,000 a year. In San Francisco, 11 of 24 buildings were leaking, 345,000 gallons and $11,040 a month, with ROI under two months (see the ROI breakdown). None of that was visible until the buildings were monitored.
The three types of apartment leak detection systems
Meter-level water monitoring
A sensor reads the building's existing water meter, or a clamp-on flow sensor reads a pipe, and software looks at the flow pattern. If water never drops to zero overnight, something is running. Because it sees every gallon that enters the building, meter-level apartment water monitoring catches leaks no point sensor can reach, including slab leaks, leaks inside walls, and running toilets in every unit.
Best for: cutting water bills, finding hidden leaks, and covering a whole building with one device per meter.
Limit: it tells you a building or zone is leaking, not which unit, unless you add zone or unit sensors.
Point-of-leak sensors
Small spot sensors sit on the floor under water heaters, washers, dishwashers, and in HVAC drain pans. They alert when they get wet.
Best for: catching water on the floor at known high-risk spots.
Limit: they only see the spot they sit on, and a large building needs many of them. They won't catch a running toilet or a slab leak because that water goes down the drain or into the ground.
Flow meters with automatic shutoff valves
A meter and motorized valve are installed on a unit or riser supply line. When the flow looks wrong, the valve closes.
Best for: new construction and buildings where stopping a burst line automatically is the top priority.
Limit: installing a valve means cutting into plumbing, so it usually means a plumber, a water shutdown, and coordination with residents.
Many portfolios combine types. A common path is to start with meter-level monitoring across every building, because it pays for itself in water savings and shows which buildings have problems, and then add point sensors or valves where the risk justifies them.
Buyer criteria: what to ask every vendor
1. What does it actually see?
Ask whether the system sees total building flow, unit flow, or only water on the floor. If your biggest cost is the water bill, you need flow data. If your biggest worry is a washer hose in a top-floor unit, point sensors or unit valves matter more.
2. How is it installed, and who does it?
This is often the biggest hidden cost. Systems that cut into pipes need a plumber and a water shutdown. Systems that read the existing meter or clamp onto the outside of a pipe don't. NOWi's Meter Monitor reads the existing meter with magnetic, pulse, or meter protocols, and the Pipe Monitor clamps onto the pipe. Neither needs plumbing work.
3. How does it connect?
Building Wi-Fi is often unreliable in meter rooms and basements, and tenant Wi-Fi isn't yours to use. Ask whether the system needs Wi-Fi, a hub, or a gateway, and who maintains them. Cellular devices connect on their own, like a phone. NOWi's monitors connect over cellular with no Wi-Fi and no gateway.
4. How fine is the data?
Monthly or daily readings can show a building used more water. Minute-level data shows when a leak started, whether it's continuous or intermittent, and whether it actually stopped after the repair. That difference decides how fast your team can find the source.
5. Who gets the alert, and what do they do with it?
Ask who receives alerts (on-site maintenance, a property manager, a monitoring center), how they arrive, and how much context comes with them. An alert that says which building and what flow pattern lets your team fix it the same day.
6. What does it run on, and what does it cost to keep running?
Ask about battery life, power requirements, subscription pricing, and what happens when a device goes offline. NOWi's Meter Monitor is battery powered with a 5+ year battery, so no one has to run power to the meter.
7. How fast does it pay back?
Ask for published results from buildings like yours, not just an average. See the ROI section below.
How the leading multifamily leak detection systems compare
Below are short, factual summaries based on each vendor's own public pages. Check current details with each vendor before you decide.
NOWi Sensors
Meter-level and pipe-level water monitoring. The Meter Monitor reads the existing water meter, and the Pipe Monitor clamps onto pipes with ultrasonic sensing. Both send minute-level data over cellular with no Wi-Fi, gateway, or plumbing. Alerts go straight to the on-site maintenance team. NOWi is focused on finding the leaks that drive water bills and catching damaging leaks early, across a whole portfolio in one dashboard.
Eddy Solutions
Eddy describes a managed water protection program that combines point-of-leak sensors (Eddy H2O), unit-level metering and shutoff (Eddy IQ), building-scale meters and valves (Eddy Link), and a 24/7 live monitoring center. Devices run on Eddy's own LoRaWAN network with gateways that backhaul over Ethernet or LTE. Eddy positions the program from construction through operations.
LeakSense
LeakSense describes flow-based leak detection for apartments with a flow meter and, where applicable, a motorized shutoff valve on each unit's supply line. It offers cellular and Wi-Fi device options, automatic and manual shutoff from a web app, and per-unit usage tracking. Its installation page describes unit-by-unit installs on accessible aboveground copper or PEX pipes.
Alert Labs
Alert Labs describes cellular sensors with battery backup and no Wi-Fi required, automated 24/7 phone call alerts, automatic shutoff valves for pipes up to 6 inches, and the AlertAQ analytics platform. It monitors leaks, temperature, humidity, and building power status.
Which type fits your building?
- Existing occupied buildings with owner-paid water: start with meter-level monitoring. It installs without residents noticing and goes after the water bill first.
- Buildings with known high-risk equipment: add point sensors at water heaters, boilers, and drain pans.
- New construction or full renovations: unit valves are easiest to add while walls are open.
What results look like in real apartment buildings
Here are NOWi results already published on this site:
- Los Angeles, 47 buildings: 72% were leaking in week one. 34% were leaking more than $100 a month. About 794,000 gallons a month (8.5% of use), about $190,000 a year. The worst building was about 7,351 gallons a day. Read the LA study.
- San Francisco, 24 buildings: 11 were leaking, 345,000 gallons and $11,040 a month, ROI under two months. A separate 27-building group showed 159,000 gallons and $5,100 a month. See the ROI article.
- One garden-style site: 1,521 gallons per hour leaking, $24,092.64 a month. Triage took 2 hours. Read the case study.
These numbers come from the same kind of monitoring: one device on the meter, watching flow every minute.
How to estimate ROI before you buy
- Pull 12 months of water bills. Look for buildings whose use is high compared with similar buildings, or rising without a reason.
- Estimate your leak share. In the LA portfolio, leaks were about 8.5% of use. Your buildings may be higher or lower. Monitoring will tell you.
- Multiply by your water and sewer rate. This gives a monthly savings range.
- Add avoided damage. One damaging leak caught early can cost more than the monitoring itself. Use your own claims history.
- Compare against total cost. Include hardware, subscription, and installation, including any plumber time and water shutdowns.
Systems that install without plumbing start saving sooner because there's no construction project in front of them.
A simple rollout plan
- Pick a handful of buildings with the highest water bills.
- Install meter-level monitoring on each building's main meter.
- Review the first week of data. Look for buildings that never reach zero flow overnight.
- Send maintenance to the worst buildings first, and use the data to confirm each repair worked.
- Add zone monitoring with clamp-on pipe sensors or point sensors where the data says you need more detail.
- Expand to the rest of the portfolio.
Frequently asked questions
What is multifamily leak detection?
It's any system that watches an apartment building's water for signs of leaks. That can be meter-level flow monitoring, point sensors that detect water on the floor, or meters with shutoff valves. The goal is to find leaks before they waste water or cause damage.
What's the difference between apartment water monitoring and leak sensors?
Apartment water monitoring watches flow through the meter or pipes, so it sees every gallon, including hidden leaks like running toilets and slab leaks. Leak sensors only detect water that reaches the spot where the sensor sits.
Do I need a plumber to install apartment leak detection?
It depends on the system. In-line meters and shutoff valves usually need a plumber and a water shutdown. NOWi's Meter Monitor reads the existing meter and the Pipe Monitor clamps onto the outside of the pipe, so neither needs plumbing work.
Does it need Wi-Fi?
Some systems do. NOWi's monitors connect over cellular, with no building Wi-Fi and no gateway.
How quickly will I see results?
In the LA portfolio, leaks showed up in the first week of data. Results depend on your buildings.
Can it tell me which unit is leaking?
A single meter monitor shows that a building or zone is leaking and what kind of leak it looks like. To narrow it down, you can add clamp-on pipe monitors to break a building into stacks, levels, or systems.
See what your buildings are leaking
NOWi helps apartment owners and operators find hidden leaks, cut water bills, and catch damage early, with no plumbing and no Wi-Fi. See how NOWi works for multifamily properties, or contact us to start with your highest-bill buildings.