I am not needing to do this, but I was curious about draining and filling for correcting CYA or maybe even CH problems. I thought I saw a post, sorry can't find it right now, talking about exposing the finish during the process and that it could cause damage. I also worry about floating the pool if the level gets too low (live in Florida, water table is really high). Can you add water while removing water? Say put the hose in the shallow end and use the main drains on the deep end to take the water out?