I'll add just a bit to the discussion. The sediment bowl can be leaking at the cork gasket, the packing in the valve, or the hose nipple. If it's just running down the glass bowl, a new gasket will probably fix it. If from the packing nut, try tightening the nut just a little at a time. The needle will get too hard to turn if you overdo it.
I found some neoprene (?) gaskets in a "SunBelt Products" catalog at my local Deere dealer. They work much better than the original cork version. I'm not a "purist" so because it doesn't leak after removing the bowl for cleaning a time or two, I'm using them.
HAPCO also sells a complete bowl assembly. The easiest way to stop the leaking at the valve is to replace the whole unit. BTDT
tommyhawk