We have a 15000 gal pool, dont know the dimensions but it is 74' perimeter and goes to 8ft deep. We are replastering and thinking of redoing the old copper plumbing. We were quoted on 3 return lines (we currently have 2) an autofill, a poolsweep line, skimmer, and split the main drain. We are kind of weary of cutting through the gunite for the main drain. Wont it weaken the shell? One pool contracter said we dont even need a main drain, that the vaccum and skimmer would be enough circulation. What are your opinions of the main drain. Should we just close it off? Thank you.