I recently failed a gas piping inspection in Seattle. I had moved a branch on an existing system and had installed a ball valve in order to isolate the extension and test only that portion. I and everyone I know has done this a million times. The inspection report said to install a Telltale tee which I, nor anyone I know and talked to, knew what that was. My best guess was to install a tee after the valve with a valve on each port of the tee. I left the supply side and the new install valves off to control the gas and the test while leaving the third valve open.. I guess this is intended to keep a failed valve used in a test from adding outside air into a gas system. I had the system inspected again, but this time I was there and of course I get a different inspector who I know and he doesn't even glance at it and we ended up talking about something else and forgot to ask about the Telltale. Anyone ever heard of this? Is this common in other jurisdictions?