I'm trying to make a 1 1/2 pvc fountain for my Doughboy pool, but I'm stumped as to how to connect anything to my return fitting. The fitting is 1 1/2 inches and is threaded on the outside, but then there is a circle of plastic at the end (sorry, don't know the term) that prevents me from screwing anything on to it. On the inside, there are a couple of pieces of plastic that look like you could connect some sort of adapter to it. I know I'm missing the return eyeball, but I just want to know how to connect a pvc pipe to this.
Thanks for any help! I've attached a picture of the return fitting if it helps.