Petcock leak

I've been riding my 79/650 everyday and enjoying my time on 2 wheels. I noticed a small leak coming from the elbow at the fuel hose. The leak isn't a drip, but enough to shine up where the 90 elbow meets up with the petcock body. The elbow slightly rotates, and I'm guessing there is an o-ring and clip on the elbow (at least I'm hoping there is).

Just want to ask if this is a common problem and if I'm on the right track before pulling it apart to inspect and correct.

This is the stock petcock with a connected vacuum hose.

Thx

The fuel nipple on mine was just press fit into the orifice (no o-ring or anything).
When it came out while removing the fuel line, I reistalled it w Permatex liquid metal.
That was several years ago --- no leaks. A good alternate product is Seal-All --- it's listed on the HomeDepot website, so I guess their stores have it.

Thanks, I'll need to pull the tank off on the next rainy weekend to do a final carb sync and will take care of the loose nipple. It started to act up after I installed a new fuel line and filter.