Water is great but if it is unexpected, not so good. Ability to be notified when you sink or refrigerator is leaking is great.
The water heater is another almost silent leaker. When it goes, you do not want to see a river running down your driveway.
We use the Samsung Smartthings hub with several water sensors attached under sink, refrigerator, washer and water heater. Other than changing batteries rarely, they give me some sense of comfort.
The hub is useful for other sensors as well.
We have a Netgear VLAN that I run some of my wired IOT devices through. The Smartthings hub is a natural, as well as cameras. These are usually wired and use IP connections. The VLAN switch segregates traffic away from you network.
As far as wireless such as Nest thermostats and Rachio lawn system, I utilize a guest channel at present.
Stacey Higginbotham has a great IOT podcast at https://iotpodcast.com/
What do you think about IOT in business and residential situations? It can be helpful but may be insecure.
Most routers have a guest channel that be used to segment the wireless devices such as Smartplugs that use wi-fi.
Use of a VLAN or virtual LAN, may segment wired IOT activity. What is your long term plan?
A newer router such as MESH type has promise to help segregate guest and this IOT traffic.
Perhaps a Prosumer router such as Edgerouter Lite which allows 2 separate LAN’s, one for personal and one for IoT devices would help your goal of separation of the streams.
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