Ask a property manager about leak detection and they'll usually describe a burst pipe: water through the ceiling, a flooded unit, an insurance claim. That's the leak everyone plans for.

It's also the rare one. The water that actually drives the bill leaves quietly — through a toilet that refills every twenty minutes, a faucet that never fully closes, a shower running far longer than it should. Nothing floods. No alarm goes off. The only sign is a water bill that keeps creeping up, weeks later, with no clue where the money went.

Good water leak detection for a multifamily building covers both problems: the catastrophic event and the silent, constant waste. Most tools on the market are built for the first. Here's how to tell the difference, and what to look for if you want to find the leaks that are costing you money right now.

Shelf one: stopping the catastrophe

Moisture sensors and automatic shutoff valves are built for the flood. A sensor sits on the floor near a water heater or under a sink; when water reaches it, you get an alert, and a shutoff valve can close the line.

That protection is worth having. But notice what it needs to work: water on the floor. A running toilet sends its water down the drain. A dripping faucet does the same. They never touch a sensor, so they never trigger one — and they can run for months.

Shelf two: finding the waste nobody reports

Silent waste stays hidden for a simple reason. Residents may hear a toilet refilling at night, but it doesn't bother them enough to call. Management and maintenance, the people who pay for it, never hear it at all. And when the bill finally arrives, it shows a bigger total — never an address.

It isn't only leaks, either. Waste has three sources:

• Leaks, which need a repair.
• Overuse, which needs a conversation with the resident.
• High-flow fixtures, which need a replacement.

A detection system that can't tell these apart leaves your team guessing.

What each leak detection method can actually see

• Inspections and dye tests catch leaks on the day someone checks. They miss anything that starts after the visit.
• Professional leak detection (acoustic, thermal) finds a hidden leak you already suspect. It misses everything you don't know to look for.
• Moisture sensors and shutoff valves catch floods near the sensor. They miss running toilets, drips and overuse.
• Main-meter monitoring shows a rise in total building use. It can't tell you which unit or fixture is responsible.
• Unit-level submeters show which unit is using more — but not which fixture, and they can't be installed without a pipe to each unit.
• Fixture-level water intelligence catches leaks, overuse and high-flow fixtures, by unit and fixture. It doesn't shut off water — pair it with sensors if you want both shelves covered.

Why stacked plumbing breaks most options

Most apartment buildings run water vertically through risers that serve several units at once. There's no pipe carrying "unit 4B's water," so there's nowhere to put a unit meter. That's why so many monitoring tools end at the building is using more water — which your bill already told you.

Fixture-level detection goes where the water is used. A small meter sits on the fixture's own supply line, so it works with vertical or stacked piping, in a 1970s garden-style property as easily as in new construction.

Find it, fix it, prove it

Find. DrizzleX measures flow in gallons on a minute-based cadence, so every water event — tiny or huge — is captured. An urgent leak gets its own email or SMS alert. Smaller issues roll into reports, ranked by cost, so maintenance goes after the most expensive waste first.

Fix. Your team makes the repair, with full history instead of just a warning. The flow record shows whether a toilet has been running on and off for weeks or started this morning — the difference between a new flapper and a new toilet.

Prove. The building main shows consumption drop on screen the day the waste stops. Then the city water bill confirms it in real dollars every billing cycle. The city says it, not us.

What it looks like in a real building

A Los Angeles property with three buildings and 182 units, built in 1988, put DrizzleX on all fixtures in June 2023. Over the next six months, consumption fell about 34% — roughly $73,500 a year, annualized. The system broke even in about eight months.

Nothing about that building was unusual. It had the same running toilets and dripping fixtures as most properties its age. The difference was that someone could finally see them.

Five signs your building has hidden leaks

1. The water bill rises while occupancy stays flat.
2. Overnight use stays high, when almost nothing should be running.
3. Residents mention a toilet that "fills on its own" — but only when you ask.
4. One building costs noticeably more per unit than similar ones in the portfolio.
5. The same fixtures keep coming back as work orders.

One of these is worth a look. Several together usually mean the waste has been running for months. For the dollar side, see what an undetected leak really costs.

See what's running in your buildings

Send us six months of water bills and your tenant count, and we'll return a per-building estimate of the waste we'd expect to find. Get Your Estimate