Figured I'd throw this tip out there..I was assembling my rails yesterday and had a couple pvc fittings that were looser than I'd like, I'm not gluing any pipes, just pressing them together. I figured out that a strip or two of teflon tape around the pvc will tighten up the joints, but still pull apart, takes a little more muscle though. I also used a set of pliers to make teeth marks on some of the pipes, makes for a tighter joint.
I'f ya don't mind spending a little extra, you could use push to connect plumbing fittings to hold all the pvc together. I priced it out and it would have been under $50 in just fittings just for 1 flowering system, but i think the added cost is worth it considering they are reusable, sealed with a o-ring and easily removable. I'd only use them on fittings outside of the res.
As a drain for the rails, the one area i think needs improvement, it should be more sealed and light proof, I am going to PVC glue 2" pvc end cap like this
on the bottom of the rail, then drill a 1.5" hole through the center. I found 2" id pvc hose that should slip over the threads and I'll put a hose clamp on it and have the hose fed through a hole in the lid. I should know by tomorrow night if it's all gonna work. I need it ready to go in 2 weeks and I'd like to dry run it for 3-5 days. I'll take pics if i remember..