Noob question: My inground pool is drained and I need to replace the liner. I also want to replace my old fiberoptic light system with a retrofit LED either from Jandy or Next Step. Both of their products say they will fit a standard 1.5 inch return fitting. I took apart the fitting face plate and pulled out the existing fiberoptic light. The diameter of the female threads of the fitting are just under 2 inches. I don't have access from the pool deck to the pipe behind it. Any idea what size?