I'm looking at the broken pieces of the nozzle thing shoots water into our above ground pool. Hopefully you know what I'm talking about. It came apart into three pieces (a ball with a hole in it, a cover piece that traps the ball, and and a piece that screws into the wall) when I tried to replace it with a screw in plug to close the pool. So I'll want to replace it next year. I'm guessing they probably come in different diameters and thread sizes, so how would I know what to order? Or should I replace the entire thing that attaches to the side of the pool that houses the nozzle? And again I know nothing about pools.