I can't answer your plumbing questions, but just wanted to throw a caution in there about the stabilizer....most people try to keep theirs in the 20-40 range. Remember that it is very slow to register (not sure about the liquid type, I've never used it) and it's easy to overshoot it. Caution is the key! THat being said, once you get your CYA into the 20-30 range, you can get an idea of how much chlorine loss you have daily, and you can always up the CYA if you feel you're losing it too quickly. I'm in Louisiana, and my pool is in full sun all day, and I find that I lose a lot less chlorine if I keep my CYA up in the 70-80 range. That's extremely high by most standards, but it's the optimal range for my pool.

You might want to reconsider taking out the chlorinator--with the waterfall in your pool, you're going to likely fight a pH rise, and while you still need to raise your CYA, the chlorinator is the ideal solution, since trichlor adds chlorine, drops pH, and adds CYA. It's also really nice for use while on vacation.

Janet