TankWatch hangs on the tank, senses when water is flowing, and sends a notification when a flapper sticks or a fill valve won't quit — before it becomes a four-figure water bill.
Join the pilot See how it worksNo hub · No subscription · 3×AA, about a year
How it works
A thin bracket slips over the tank wall — the lid still seats. Nothing goes in the water. The sealed body hangs outside the tank, so changing batteries never means reaching into a toilet.
Scan the code under the lid, pick your WiFi in the app, done. No hub to buy, no cloud account it can't live without — the beeper works even if your internet doesn't.
It sleeps almost all the time, wakes when the tank does, and checks in with battery status along the way. You'll hear from it when something's wrong — and only then.
The ten-minute rule
Every flush makes the tank refill for a minute or so — that's normal, and TankWatch stays quiet. A running toilet never stops refilling. Flow that won't quit is the tell, and you choose how long is too long.
Chirp in the bathroom. Notification on your phone — even if you're out of town. That's the whole product.
Honest hardware
There's nothing exotic inside and nothing in the water. A single sensor tells a microcontroller when the tank is refilling, and the microcontroller does the arithmetic. Fewer parts, fewer failures.
| Radio | 2.4 GHz WiFi (joins only to send) |
| Batteries | 3 × AA lithium |
| Battery life | About a year typical |
| Check interval | Adaptive — more often while the tank is active |
| Alert threshold | Continuous flow past your limit (10 min default) |
| Local alert | Piezo chirp, ~70 dB |
| Heartbeat | Twice daily with battery status |
| Fits tank walls | Up to 30 mm, lid stays seated |
| Enclosure | Moisture-rated PETG |
| Subscription | None. Ever. |
Hall bathroom has been running for 10 minutes.
TankWatch · nowQuestions
Because the expensive failures are the quiet ones — a flapper that seals almost, a fill valve trickling into the overflow tube. TankWatch senses the refill itself, whether or not you'd ever hear it. It also notices a tank that refills in the middle of the night when nobody flushed.
No. Each unit joins your home WiFi directly and only powers its radio when it has something to say. One device, one battery set, one job.
The local chirp still works — detection happens on the device, not in a cloud. The notification catches up when your connection returns.
The bracket clears tank walls up to 30 mm — that covers nearly every residential tank — and the lid sits back down over it. If yours is unusual, the pilot is exactly the place to tell us.
Red Zone Enterprises, a data-reconciliation consultancy in the DC corridor whose reputation is built on one promise: the reports will be right. TankWatch is that promise, pointed at your water bill.