I have a 30 year old pool (age approximate) 20 x 40 in ground. The pool is on a sloped grade so that the water level at the shallow in is at ground level and the water level at the deep end of the pool water level is about 3 feet above ground level. (lots of concrete) The main drain at the bottom of the deep end has been plugged for at least the ten years we have owned the pool. It looks like the deep end settled at one time and the previous owners fixed the pool but not the main drain. We have to vacuum the pool a lot. Anything the settles to the bottom stays there. I am wondering about replacing the main drain. What are my options?