Advice for horizontal nipples in pvc

[jbofky]

I raised two Salatin-style pens of Cornish last year and loosely copied his waterer design. I used a 5 gal bucket on top of the metal with quick release air hose fittings. Ran a piece of tubing down to a 5' piece of 1" pvc. I installed Solway horizontal nipples in the pvc and glued a ball valve at the end to flush it with. I noticed that some days that would drink more than others but I went out one day after work and found that they had pulled a nipple out of the pvc. I found that there was still a half full bucket of water but it wasn't dripping. The kids just rest loosely on top of the buckets to keep out debris. With the top completely off, there was still no water dripping from the open hole or from the ball valve. No kinks in the hose. There was some funky vacuum lock going on so I switched them to buckets with horizontal nipples inside the pens.

Does anyone know how to remedy this?

Also, I have a terrible time getting them to seal in the pvc. I've never had any trouble in buckets but they kept wanting to strip and push out of the pvc.

What do I need to do differently with that?