I woke Friday morning to a partly flooded basement due to the water heater leaking. I will be putting a drain pan under the new water heater to prevent the basement from flooding again. However, I’d also like to put a leak detector in the drain pan and have Alexa, Google or HA to send me an alert or notification that a leak has been detected.
Anybody have a recommendation for such a device?
I have the Aqara ones and the IKEA Badring connected through Zigbee, and the new IKEA Klippbok connected through Matter. All work when I remember to test them from time to time.
I’ve got quite a few leak sensors – one under every water-using appliance or fixture. (And a whole-house water shutoff valve that can be triggered by automation).
I’ve got several different brands and models; mostly Aqara; all work well. Some Z-Wave, mostly Zigbee. Batteries last a really long time; most of mine have been here for years, & I don’t think I’ve needed to replace a battery yet. I don’t do any regular testing (but maybe should); I just make sure they stay online in HA. Anytime one’s gotten wet, from actual water issue, or cleaning, or puppy saliva 
, they’ve responded.
Similar experience. I have tried a handful of those and have not run into any I would not recommend.
There are 2 main styles, though - (a) one style has 2 probes and is designed to detect continuity (aka water) between the 2 probes, and (b) there is another style that comes with a “rope” or “string” where the trigger would go off anywhere the rope gets wet.
OK this is interesting. I googled around and see Sonoff SNZB-05P can do both. Not affliated.
Oh and, technically there is yet another (more complex and expensive) style (c), where you attach a flow senser to your pipe, and the flow sensor would obviously track your household water usage over time, and would be sensitive and smart enough to tell regular water use vs small, constant, potential leaks. This style (if tuned well) would help detect leak but would not tell you where, though, but would be the only solution to tell you have leaks somewhere behind the wall.
This 3rd style probably is not for your use case, but it’s out there.
I can vouch for the SNZB-05P specifically — though I should be straight that my incident was smaller than yours. Ours is a little under-sink hot water unit, the kind you use for drinks and washing up, not a whole-house tank. It started leaking and the sensor sitting beneath it caught it, so we got the notification while it was still a leak rather than a flood. Different scale, same reason for having them.
I run five, one under every sink. Zigbee, straight into HA, no cloud or vendor app in the middle. They take a CR2477 and I haven’t had to change one yet.
For a drain pan specifically, I’d get the version with the detection cable rather than a puck with two contacts on the bottom. A pan fills unevenly and won’t always wet the exact spot the sensor happens to sit on — with the cable you can run it along the low edge and catch water wherever it actually pools. Same reason it’s useful behind a trap or under an appliance you can’t easily reach.
Worth saying: they do nothing for months and then justify themselves in a single night.
I like zooz for leak detectors. I had shelly (prior generation) and their batteries tended to go from around 80-100% to zero instantly, so I never got a warning before they went unavailable (I have a warning at like 35%). That just seemed unacceptable so I trashed and replaced them.
I also recently added a whole-house cutoff valve (well, replaced the twist on there with a ball valve) and added a zooz controller for it, so now if any of the many leak sensors alert the house water is cut off.
Murphy dictates if you have a leak, you will not be home when it happens (or you will be sound alseep and not notice your dashboard or phone alerts).