I have used three brands of threaded red plastic screw in nipples. I have drilled the right size hole in PVC, used silicone when installing, drained the system for winter... Basically done everything right. The problem is that the poor little nipples have a bunch of greedy chickens pecking at them all day just trying to make the seal fail. So I am stepping it up a notch. Last week on amazon I got all stainless steel nipples. Body is stainless too. Including shipping they were almost 3 bucks each- well worth it if this is the last watering system I have to build. The threads are 1/8" NPT (national pipe thread). This time around- I'm ditching the soft crappie PVC pipe in favor of 1/2" aluminum or galvanized pipe. Each hole will have to be drilled and tapped for the threads to screw in - making them serviceable and re-sealable. Has anybody else gone this route? Any advice would be appreciated. I will let y'all know if it works!