Just remember that both zwave and zigbee are MESH networks. As such you need to think about making sure the mesh is strong/built correctly. Typically that means you will need some NON-battery powered devices to act as repeaters.
A few plugin outlets can work, for example.
If you do only battery powered devices you may find that there are issues with them dropping off the network, or not updating as you expect.
Although it is very inexpensive, I cannot recommend the Xiaomi/Aqara Zigbee water leak sensor.
I have tried every trick in the book, but they continually fall off my Zigbee mesh.
I have tried extensively to establish a strong Zigbee mesh, with exactly the right kind and location of repeaters.
Maybe others have had no issues.
(Others have connected these devices to a Xiaomi gateway.)
I have had no end of issues.
There was some rumor that Aqara was coming out with a true Zigbee 3 compatible line of devices, but there has been no such product to buy yet.
I too use the Samsung water sensors. I like the upper and lower contact sensors. I have 12 of these near every potential valve/water source (sinks, toilets, laundry, fridge, water heater) and have an automation to turn off the water main using a Dome shut off valve. As a test, if I run the faucet, and trigger a sensor using a wet finger, the water will stop running in less than 10 seconds. As a bonus, I use the Chromecast integration to have an announcement made which water sensor was triggered.
Good points. I was hoping to start with a strong z-wave mesh, as my first two control points are with z-wave switches. Since I will be using several water sensors, eventually, I will need to get both meshes in place.
Yea, mine is pretty tight. I had to keep the access door open in order to give the Dome clearance to close the valve. Maybe there is somewhere downstream you can add something similar? For me it was a must as I am away from home 10-12 hrs a day and if a leak happened I'd want an immediate shut off