Return pipe pressure relief is leaking?

[mich.bell]

Hi there. After hearing a dripping next to our pool, we discovered that one of the return pipes seemed to be leaking. The pipe goes to the jet, but there is a section of pipe that goes above the jet, makes a 90 degree turn, and then ends. That's where water is dripping out of. If we plug up the jet, it leaks less. With the pump on, it leaks more. It doesn't look like anything had been connected to this end - the inside of the pipe is clean. I read somewhere that sometimes these exist for pouring antifreeze in for winterizing (although it probably only gets below freezing once every couple years here). There was some other reference to pressure relief, but in either case, why would it be leaking all of a sudden? And how do we fix it? Thanks in advance. (I'll try to attach an image, but need to figure out how to do that on here...)

[Teapot]

I haven't a clue why on a open system return you would have a pressure release valve or even a point to add antifreeze (drain the line). Is it a air in venturi to make bubbles from the jet? Photo?

[mich.bell]

So once we were able to get underneath to see more, what it looks like is an overflow pipe - what we thought was a jet is not, and the pipe goes just higher than the water level is, and there's nowhere else it goes to. It's still strange that it just ends right there and there isn't something that directs the overflow away from the pool, so we might do that just to be safe. Also strange because there's another overflow hole/pipe where the water leveler float is. But unless this still doesn't make sense to anyone, I think we are good to go. Thanks for the reply!