So, a little backstory...when we bought our house a year and a half ago (with in-ground 25,000 pool) I asked the previous owner how many returns were supposed to be in operation. At that time there were three "returns" in the pool, but only two had eyeballs on them and were actually functioning. He said that the two with eyeballs were the only ones and he didn't know what the other was for.
Fast forward to today and I finally got around to trying to figure out a dead grass spot right next to my pool deck. I figured the grass was already dead so I took a shovel to it and after a couple of moist shovels of mud, I hit water. Long story short, after much careful digging and investigation I came upon a 1-1/2" pvc pipe with no cap on it. Towards the end I was digging with my hands and pulled out some wax-like paper and that's when the water really came a-gushing. I'm assuming that somebody had stuffed or wrapped the end of the pipe in something and then forgot about it. I should mention the pipe leads towards the pool right where the "dead" return is.
My questions are: is this common and why didn't they hook up the 3rd return (maybe it was for a vac line that they decided not to use)? Is there any benefit to having it hooked up (since I've already gone through the trouble of digging it up)?