Node / Pipe is not connected to, or is isolated from, a boundary (reservoir or tank) user notification
This user notification indicates that there is not a physically connected source of water to supply the nodes indicated by the message.
1) Right click one of the user notifications about the node not being connected to a boundary element and choose to "Select All Elements with Message ID 41595".
2) Right click one of the elements in the drawing pane and choose "Create a selection set" of all the elements
3) Create a new color coding for the junctions based on "Is Active?" (or any other attribute that is the same for all the elements) and only color code the elements in the selection set you made in step 2. This will let you see all the elements that are not connected to a boundary element more easily. You can also consider color/size coding pipes on "Is Closed?" to make closed pipes easily visible.
4) Locate the source(s) of water in the model. For example, you could set their symbol size larger, set the style to GIS or do something similar to make them more visible.
5) Locate inactive pipes by going to Tools > Options and on the Global tab change make sure the "Display Inactive Topology" checkbox is checked and set the color to something identifiable. Go back in to the model and locate if there are any pipes that connect to the water source that might be cut off by this pipe being closed with no other source of connection.
6) Go to View > Network Navigator and click the " > " icon. Choose "Network Trace" > "Trace Downstream". Select the reservoir or tank that is the upstream element to start tracing from.
7) In Network Navigator click the pencil (marker) icon that is located to the left of the two green arrows (refresh drawing) icon. This will highlight all of the downstream elements
8) Look closely at the highlighted pipes/elements (connected to the boundary) along with the colored junctions (the isolated elements) and you should be able to locate the disconnect. For example, there might be a pipe that appears as if it's connected but is only crossing over another.
9) If there is a valve at the boundary of the disconnected pipes/nodes then make sure the correct Downstream Pipe is selected.
If you have more than one boundary/source, you may need to repeat steps 4-9 for each.