Under "normal" operations this one doesn't drip much if any. I usually clean it out about every 4-5 sessions whether it needs it or not. It rarely builds up much if any debris as I only put in clean very fluxed lead.
Before I started using it for casting bullets I tore it down and used a couple of different grits of lapping compound to lap in the seat and stem so that they are matched. This alone helped tremendously.
Actually my original use for that pot was to pour up large wire legged weights to be used in the surf for shark fishing. I used some scrap SS and copper tubing I got from work as the outer body and the finished product came out between 1 & 2 pounds depending on which type I made up. That is why the whole thing was raised up an extra 2" higher than when it was shipped. That being said the extra height also helps to see what's going on with the molds a LOT better than in the original form.
About the only time this one drips is during the initial melting of the alloy if I leave it more than half full. I guess as the lead expands when it heats up, it pulls the rod up just enough to alloy things to get slip through. This particular picture was the result of turning it on, then getting an unsuspected call from nature, that took longer than expected.