The pool where I work was built in 1970 with concrete and a ceramic tile surface. It holds 100,000 gal and has a single main drain which is gravity fed to a D.E. filtration tank that has a max output of 225 GPM. The main drain is about 27"Lx22"Wx24"D When the pool was drained to replace the lighting, the old metal sump was so rotten that it literally vacuumed out by shop vac. A 6" pipe leads under the pool to the filtration room at the end of the pool.
I assume we'll fabricate a new sump inside the dimensions of the old (but the same depth) out of poured concrete. We could drop in a fiberglass/plastic ready built unit, but either way, I have the same question.
If we are to install a new sump, how do we create a watertight joint both to the old concrete as well as to the old pipe?