It seems that our pb went away. Our initial code was closing connections only (in the finally clause) assuming that this will de facto close it. It seems that it's not enough for this pool. In also closing resultsets and prepared statements, our leak is now gone. Apparently some non closed objects in the connection prevent to close it properly. View the original post : http://www.jboss.com/index.html?module=bb&op=viewtopic&p=3986900#... Reply to the post : http://www.jboss.com/index.html?module=bb&op=posting&mode=reply&a...