@Interplaydave 

As long as the device has a Zigbee antenna it should work. The level of control may differ as far as features that are available.

Thanks Tony . . . Many of the water controllers come with a separate hub. This hub connects usually via wifi to the router.  I know this would work, but want to leverage the built in hub.  If I understand correctly, as long as the water controller itself has a zigbee antenna then you can connect it directly to the M9 Plus hub and bypass, or not use, the hub that comes with the water controller. Can you confirm?

Many thanks . . . 

@Interplaydave 

Correct, once the water flow controller is connected to the Deco you should be able to control it from Deco app.

Here is an example of adding a Securifi Motion Sensor:

https://www.tp-link.com/us/support/faq/1784/