Isolation trace returning incorrect results

[EC1]

Hello

I am working on a Water Utility Network Model, which include the following features: Water mains, Water meters and Isolation valves.


I have created a isolation trace that selects water meters impacted if that water main had to be shut off using the nearby isolation valves. This trace works 95% of the time when run. But occasionally it will instead return the whole network of water meters. I have been trying to work out why, but so far I have not come up with any conclusion. 
I have checked my topology rules and everything seems fine, which makes sense, because this trace works in the majority of the cases. 

When I run a connected trace on the same areas with issues, instead of an isolation trace, I get the appropriate results. see example below. note that the example below shows selected isolation valves instead of water meters, but the issue is the same.  

above images description: Connected trace, condition barriers: isolation valves, output: isolation valves. (Include barrier features is on).

above images description: Isolation trace, Filter barriers: isolation valves, output: isolation valves. (include isolated features is on)

as can be seen the connected trace returns the appropriate selected isolation valves (5), while the isolation trace returns the whole network of isolation valves (1000+). I need to use the isolation trace specifically for the include isolated features function, to define the shut-off blocks properly, rather than a connected trace. 

I am truly stumped by this issue. Any recommendations of things I could try/check would be greatly appreciated.

[MikeMillerGIS]

Is there anyway you can share your data?  I am not sure without looking at it.  If you cannot share, can we find a time to do a share share?  You can email me at mmiller@esri.com.

[EC1 · Accepted solution]

Solution found:

There were some scour valves which had incorrectly connected directional terminals, nearby the areas which returned the whole network incorrectly.

In the areas with issues the startpoint/endpoint of the pipe was not connected to the appropriate terminal. For example the from terminal was connected to an end of a water line, rather than a start of a water line. My guess is this incorrect assignment caused the trace to return the entire network, ignoring any more condition barriers (isolation valves) it came across.