Problems in the Pipes?

Ok, best title I could come up with for a few basic questions. Here goes.

I have a 20,000 pebble-tec pool with pentair pump/filter/swcg. The pool has a cartridge filter system, two drains, probably 8 jets, a cleaner hookup, and skimmer. I let my dog swim in the pool pretty often right now. Is this a terrible idea? I figure it just means I have to clean the filter a little more and the drain tends to collect her hair after a long swim.

When I do find hair collected on a drain, it seems to collect pretty consistently on the same one everytime. We're talking quite a handful of hair on one drain, and the other one squeaky clean. The two are both located in the deep end of the pool, seperated by only about 4 feet. At least I assume they're both drains, any ideas? Or a way to check suction on the other drain?

And lastly, my pump tends to lose its prime when changing the valves for either the skimmer or the cleaner. If 0 is skimmer/cleaner closed with drain/feed open and 180 is skimmer/cleaner full open with the drain closed, moving either valve past 45 causes the pump to lose its prime. Is this normal?

Really glad I found this forum, I'd be lost to the grips of a pool store if not for you all. Thanks in advance... Really!