SensingDesign complete (stages 1–6), not built, not certified

WaterLeak Building

Supervised leak sensing for buildings, and a TankWatch kit for the water heater in your home

Finds water under water heaters, sinks, washers and in pipe chases across a whole building, alerts the on-call team, lets the manager close a listed valve on the affected riser, and keeps a tamper-evident log.

Who buys it: Property managers and owners of multifamily buildings (20 to 300 units) and small commercial buildings.
Why it pays: A leak caught in minutes stays in one unit instead of soaking the floors below (multi-unit losses often $20k to $50k or more, est.); a 96-unit building costs about $9k installed + $144 a month, against $50k to $200k for per-unit shut-off devices.
Target price: Sensor $29, valve node $199 (valve and plumber extra), LTE gateway $349, $1.50 per apartment per month (target); TankWatch home kit $69 (target)
First-minute wow: A floors-by-risers grid of the building where a wet sensor turns its unit red, and two wet sensors on one riser bring up a 'close riser B' card naming the units that will lose water.

See the CAD design Concept page

WaterLeak Building concept: the idea and where each part goes — The concept. The CAD design is below, under Printable CAD.

What the research found

And how this design answers it

Home water heaters (R8, 26 Oct 2026): the 56 mm sensor cannot fit in the 25 mm ring between tank and pan → TankWatch pan finger puts the pads on the pan floor, and pipe clips catch a dripping relief valve, night hot-water use and freezing
$16 Govee and YoLink sensors → sells the supervised building system (heartbeats, mapping, escalation, valve, logs), not the sensor
Insurers give single-home shut-offs away → works at riser and branch level for buildings with shared risers, and exports logs for brokers
Camera and NPU on battery wasn't credible and invaded tenant privacy → camera removed; contact pads, rope and humidity on 2×AA for about 5 years
Unreliable tenant Wi-Fi → LoRaWAN through floors to a property-owned LTE gateway
Shut-off liability → listed potable valve on domestic lines only, never fire lines; two-signal rule or manager confirm; fails as-is

Use case

Riser joint fails inside the pipe chase

Property managerOn-call technicianPlumberTenants on riser B

01Trigger: a fitting on riser B fails between floors 5 and 4
02Detection: chase sensors in 502 and 402 go wet 6 minutes apart and the riser meter shows burst flow
03Alert: 'Riser B leak suspected' with a tap-to-close card to the manager
04Action: the manager taps close, the valve node shuts the listed valve and confirms it, tenants get an SMS

Outcome: Water off to one riser 10 minutes after first detection; riser A keeps water; damage limited to two chase walls instead of several units (est.)

How it works

Architecture

01
Sense: RAK3172 spot sensors with stainless contact pads, optional rope and SHT40; valve nodes read meter pulses and valve position
02
Decide: sensors wake on water with no polling; valve nodes enforce relay interlocks and authenticated commands
03
Send: LoRaWAN 915 MHz to RAK7268CV2 gateways with LTE backhaul, then ChirpStack and MQTT
04
Tell: rules for wet, riser leak, night flow, burst, freeze and offline; escalation, floor-stack dashboard and hash-chained reports

Hardware

Real parts, buyable today

Bill of materials: about $17 per sensor, $51 per valve node (excluding valve) and $249 per gateway at qty 10–100 (est.); TankWatch home kit about $32 at qty 100 (est.).

Block	Part	Why this part
Radio + MCU	RAKwireless RAK3172 (STM32WLE5 + SX1262)	LoRa through concrete floors; runs straight from 2×AA
Water sense	2× M3 A2 stainless screws as pads + M8 rope input	Interrupt on wet with a 0.35 mm gap; cheap and field-replaceable
Valve	Belimo B2100PW-Q + LRX24-3-S (NSF/ANSI 61 + 372 per listing)	Listed potable valve with position feedback, fitted by a plumber
Node power	TI LMR36006 from a listed 24 V Class 2 transformer	Runs from 24 VAC or DC; no mains in the printed box
Gateway	RAKwireless RAK7268CV2 (LTE)	Off-the-shelf, owned by the property, independent of building Wi-Fi
TankWatch (home)	3x DS18B20 stainless probes + printed pan finger on the rev A sensor	Pan water, relief-valve drip, hot-water draws and freeze from one battery sensor

Mechanical

Printable CAD

10 parts, generated from code and checked as closed solids. Pick a part to inspect it, or download the STL files to print.

See the CAD parts render

WaterLeak Building printable parts, rendered from the CAD — Render of the printable parts from the actual CAD. Not yet printed or photographed.

Loading the CAD…

Real CAD · drag to rotate · scroll to zoomReal CAD · swipe sideways

Open risks we are working on

Property managers may buy from bundled smart-apartment platforms instead of a single-purpose vendor
Riser valves need plumbers, permits and owner sign-off; install friction may stall deals
Concrete floors may need more gateways than planned; a site survey sets the count
YoLink or SmartRent could add riser-level valves and logs
TankWatch: whole-home leak and flow brands (YoLink, Moen, Phyn) could add a pan probe; heat-pump heaters may need tuned thresholds

Design stage only: nothing on this page is for sale. Specifications and prices are targets.