Water leak detectors for the basement: smart, with an app – and where they stop.

Two metal contacts sit on the underside. Water closes the circuit and the device triggers: a loud tone, a push message or both. Homematic IP states that its water sensor triggers from 1.5 mm of water – a thin puddle is enough.

Some models use a sensor cable instead of contacts on the housing, which you run along the wall or around the boiler. The Eve Water Guard comes with a two-metre cable that, according to the manufacturer, can be extended to up to 150 metres. It runs on mains power, though, not on a battery. That covers a line instead of a single point.

What a water leak detector cannot do: shut off the water. It reports, nothing more. If you want the supply closed automatically, you also need a shut-off valve – and someone or something that acts on the alert.

Alarm path. Siren only, app only, or both? You rarely hear a basement siren from the living room, and never from holiday. If the house stands empty at times, you need a message on your phone.

Hub or no hub. Zigbee, Homematic IP and Bosch detectors need a hub. The Aqara water sensor, for instance, uses Zigbee and reports nothing without one; Bosch states that its water detector only works with the Smart Home Controller. Wi-Fi detectors manage without. If you already run a system, it makes sense to stay in it.

Battery. Radio detectors last a long time – Aqara quotes more than two years on a CR2032 for its water sensor, Homematic IP typically five years, Bosch less than three years. Wi-Fi models need more power. What matters is that the device warns you before the battery dies.

Power outage. The detector itself keeps running on its battery, but the router, hub and internet connection do not. If the power fails, nothing is left of an app alert. And with heavy rain, the two like to happen together.

Sensitivity and form. Contacts on the housing cover a point, a sensor cable covers a stretch. For a laundry room with a sloping floor, the cable is often the more honest answer.

How individual devices fare is in the comparisons: Bosch Smart Home, Homematic IP, FRITZ!Box, Aqara, Eve Water Guard, Tuya, Shelly Flood, Fibaro Flood and Grohe Sense.

Water runs to wherever the floor is lowest. A detector in the middle of the room therefore often reports later than one in the right spot.

• Next to the washing machine and dryer – burst supply hoses are the classic case
• Under the boiler or hot water tank – these usually drip long before they run
• At the heating system – leaking fittings show up on the floor first
• In front of the floor drain – when it clogs, the water stands exactly there
• At the lowest point of the room – check with a spirit level or a splash of water if in doubt

Not useful: the detector on a pallet, on a shelf or on a step. It then reports only once a fair amount of water is already in the room. And it does not belong in the pump sump: there is water there in normal operation, so the detector would trigger constantly.

Every water leak detector needs water at its contacts. With a burst hose that is early enough – the water arrives where the detector lies, and the damage stays contained if you are quick.

In a basement with a pump sump or lifting station, it works differently. There the water first rises in the shaft, often over hours: the submersible pump has stopped, the float switch is jammed, the power is out. Only when the shaft is full does water reach the floor – and that is the moment the detector speaks up. By then the basement is already wet.

What is missing during those hours is the level in the shaft. A level sensor measures it continuously and reports when it rises above your threshold – before anything overflows.

That is exactly what Drainbee does. A hydrostatic submersible probe hangs in the shaft and measures the level up to 1 metre to within ± 1 cm, adaptively every 10 seconds to 5 minutes. The wall box sends data over Wi-Fi (2.4 GHz) to the cloud. The app shows level, pump cycles, inflow and the rain and inflow history. Alerts cover threshold, power outage and Wi-Fi loss – as a push or a call-style alarm in the app. €298 one-off, no subscription.

For smart-home users: Drainbee has a local interface (API) on your home network. A GET http://<device-IP>/status returns the current level as JSON, for example {"measurement":{"cm":27,"ageMs":3200}} – read-only, no login. You can pull that value into Home Assistant (REST sensor), ioBroker or Node-RED. The device does not push alerts into the home network, and there is no native integration with HomeKit, Matter, Bosch, FRITZ!Box or Homematic.

The two work best together: water leak detectors at the washing machine, boiler and sink, a level sensor in the shaft. One reports the leak, the other the pump.