Water Leak Week – Switchbot, Sonoff and more…


Not sure why two companies I know, decided to introduce water leak sensors in the middle of summer – but I’m happy to do a quick write-up – as it happens I’ve just recently refitted a hot water tank complete with rather large calcium filter and I’m not 100% sure of my engineering skills so – here goes:

Switchbot Water Leak Detector (Bluetooth)

Just about now, Sonoff are releasing their SNZB-05P Zigbee water leak detector and SWV smart water valve – more further down. See July 10 update at the end…

In the meantime, Switchbot sent me their latest “Switchbot Water Leak Detector”. It’s a small unit with integral beeper and self-test button – handy for a quick test after installing.

There are two stainless prongs at the front and two at the back and a text button at the front. Pressing the button gives off a fairly quiet alert, good for probably a couple of metres – I guess that’s intentional.

Switchbot Water Leak Detector

Sticking a damp finger across either of the stainless pairs lets off a much louder alert which stops immediately the source of moisture is removed. The unit looks substancial and takes a pair of (supplied) AAA batteries. As this is new I can’t comment on battery life as this would be a combination of standby current and what kind of batteries you use. When the battery is low or damp is detected, their APP will put up a low-battery notification and optionally send an email to a destination of your choice.

The manual is interesting, showing examples of places to position the unit, one example being in front of a toilet. Now, I was about to be sarcastic here when I noted that the unit does have a silicone seal around the base which you remove to change batteries.

Switchbot APP

Good idea – I can think of several local pub men’s toilets which could make use of this – it seems that significant portions of the male population can’t aim. Other examples included under a pipe bend and in the corner of a room on the floor. Switchbot are claiming 2 years battery life without making recommendations as to which brand of battery to use.

The only problem I initially found with all of this was that the unit seemed as if it was going to communicate by Bluetooth as the manual states you need to have a phone with BT4.2 or later. In my building that would be good for maybe 2 rooms between my phone and the unit – I’ve never had a great deal of luck with Bluetooth and range.

But hold on – later in the manual is a reference to the unit connecting to WiFi. Ok, long-press the test button and sure enough – pairing mode…. OK so the Bluetooth was just to get the pairing running. I turned on the Switchbot APP, hit + and immediately the water leak detector signed up and reported safe….OK I could see that being useful.

It is worth noting that unlike the Switchbot thermometer – this device did not show up in my Home Assistant network. There’s also a reference in the manual about using the detector for DRY detection using the “extended probe” inserted in a fishtank. Well, I didn’t get any kind of extended probe in the box!

The unit measure 78mm by 39mm by 32mm.

Sonoff ZNZB-05P

Ok, I’m at a loss initially…here’s what you get in the pack… the main zigbee sensor unit uses a supplied CR2477 battery (I wish designers would stick with CR2032 and other more common batteries – I have no CR2477 batteries here at all – good job one was pre-installed). I’m sure the Sonoff site adequately covers usage with the eWeLink APP but here I’ll just mention installation into Zigbee2MQTT as that is what I use.

Sonoff ZNZB-05P

Ok, SNZB-05P paired with Zigbee2MQTT. I last updated my Zigbee2MQTT a few days ago – and the response to this unit is “unsupported” – not surprising as it is new – HOWEVER despite that it does accept the unit – see the image below – wet finger across the two contacts – and I get a response immediately – see ALARM 1 below in the Zigbee1MQTT web UI.

At first glance, let me say this unit is WELL SEALED – the only metal bits being the short gold sensors – I see nothing that would indicate anything other than perfect performance on a wet floor – read the Sonoff information in the link above – they really do go into detail.. knowing where to start – there are so many places in our home that COULD leak.

Thanks to running my Zigbee2MQTT installation in Docker on the Raspberry Pi using Antonio Fragola’s Docker setup and shortcuts, updating Zigbee2MQTT is merely a matter of navigating to the DockerIOT/Zigbee2MQTT folder and keying in DUPDATE in a terminal. Seconds later – done. The SNZB-05P entry still says “unsupported” at this time (not that surprising given the newness of the device) – but still continues to work and respond to ALARM 1 as above.

Sonoff are CLAIMING a 5-year battery life using that CR2477 – I can only hope they are right (clearly not tested for 5 years as it’s a brand new device).

When I checked my Home Assistant devices list, the SNZB-05P has magically appeared with an “automatically generated definition”. Again in Home Assistant, under “entities” it looks like everything is in there – see image below….

and as I sit here, pressing my wet finger on and off the gold contacts – Home Assistant knows all about it (quick click on the “tamper 1” entity reveals all). Good start – I just need a quick Home Assistant automation to DO something with that. As the unit has no audio output, sounding a bell or alerting my phone (or both) seem like sensible options


I’ll leave the extension lead for another time – not seeing the point of a USB-C connector in a damp environment but no doubt I’m missing the point…

See also Antonio Fragola’s comment below about cheap AliExpress-sourced CR2032-based sensors. Now, if I could time travel and confirm the 5-year claim for the Sonoff unit, I would say “you get what you pay for” but I can’t time travel to confirm or otherwise 🙂

Sonoff have just confirmed that the unit does not use more current when wet, so I now have a plan to use it upside down on the inside edge of our pool frame – to check for over-filled pool. Good one.


7 thoughts on “Water Leak Week – Switchbot, Sonoff and more…

  1. Isn’t the USB cable used to detect moisture too? Meaning it sucks up the water and triggers based on that. So you don’t have to place the main unit on the correct side of the washing machine (and hope the water won’t run in the other direction), but you can place the *cable* around the washing machine and it triggers when water touches the cable!

    Eve introduced that several years ago for their homekit only sensors. Great to see sonoff is following! (At least if I interpret their website correctly)

  2. As an alternative, I use the IKEA ones with zigbee linked to HA via z2m. They use a AAA battery and work well.

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