Several months ago I posted about a NumberOfReclaimedConnections performance counter.
http://drowningintechnicaldebt.com/blogs/davidstrommer/archive/2006/11/10/Connection-Pool-timeout-expired.aspx
Today while troubleshooting another problem related to connection pooling and the datareader, I noticed that the performance monitor "add" button for the SQL Data Provider counter was disabled.
You must add the following to your app/web config file to enable them:
<system.diagnostics>
<switches>
<add name="ConnectionPoolPerformanceCounterDetail"
value="4"/>
</switches>
</system.diagnostics>
Activating Off By Default Counters: http://msdn2.microsoft.com/en-us/library/ms254503(vs.80).aspx#ActivatingOffByDefault
Angel Saenz-Badillos on ADO.Net Peformance Counters: http://blogs.msdn.com/angelsb/archive/2004/08/02/206470.aspx