Chuckie -
My old main drain did not work. Having a new main drain was not a requirement. The PB gave me two options:
1. Fill in the existing single main drain hole. No more main drain.
2. Install a dual main drain. The dual main drain consists of a single 2" or 2.5" pipe going from the skimmer to the bottom of the pool. Then at the bottom of the pool, it T's out into two drains that are at least 3ft apart. In order to get the pipe from the skimmer to the bottom of the pool, they jack hammered out some of the gunite. They left all the rebar in place. Then they put in the pipe, and then fill the hole with concrete.
I ended up going with a new dual main drain system because the project manager said that the main drain does help keep the pool cleaner and helps with water circulation. Cost of doing it was $600 to dig a new line and $300 in parts.
Minh