Water Isolation Trace "No valid subnetwork controllers found"

[Andy_Morgan]

Before I deploy our Water UN to production, I'd really like to understand what's needed to get isolation traces working. No matter what Tier I try (Water System, Pressure or Isolation), it always fails with "ERROR 001797: No valid subnetwork controllers found." Same thing happens even with the ESRI Foundation GDB (v 4.1) that I used as a starting point to build our UN.

It should be simple: System Valve / System is assigned "Isolating" Category, so all of those systems valves should act as barriers for such a trace if Filter Barrier is Category = Isolating, right?

I see the Subnetwork Controller for the Water Isolation Tier is System Valve / Isolation Zone (which I do have some in our system), but how does this relate to running isolation traces anywhere throughout the network?

@RobertKrisher wrote this: "You can always run an isolation trace by using a filter function barrier to define criteria for isolation." (https://community.esri.com/t5/arcgis-utility-network-questions/a-few-subnetwork-questions/m-p/147408...)

What does that mean? I tried adding this:

• Filter Barrier: Category = Isolating
• Filter Function Barrier: Count, Asset Group = 2

...but it still throws the same error message. 

[Andy_Morgan]

@gis_KIWI4, thank you so much for this simple point about needing to traverse the entire network! I only wish I had focused on it sooner. @MichaelParma, I also owe you thanks, since you sort of wrote the same thing. It was the words above, "needs to traverse the network before", that stuck with me, though.

I've finally realized that on the Water System tier I hadn't established a subnetwork controller, since we didn't carry in a point for treatment plants or bulk meter. Using a FGDB copy, I've managed to get things working by...

1) Creating a Transmission Main that connects to a new point of Supply / Treatment Plant.

2) Defining the treatment plant as a subnetwork controller (port 2).

3) Tracing the entire system (Tier = Water System) using a Connected Trace.

4) Running an Isolation Trace using a random starting point, with Tier = Water System and for Filter Barriers I used Category = Isolating. It successfully stopped on the first set of valves going outward from the starting point. Woohoo!