Pool overflow drain?

[tkdtime]

Hopefully the great wisdom of this board can help me identify the line/drain pictured. It is right at the top of my liner about a couple of inches below the coping in the deep end of my pool near our diving board. I've seen examples of an overflow drain that has a grate over it, but I'm wondering if anybody has seen this particular version. If it's not a drain, does anybody have any idea as to what it is?

It is a threaded pipe with a cap in it at this time. I unscrewed it and water drained into it, but I quickly re-capped it since I wasn't sure...

[attachment=0:1tknbua5]IMG_20130211_100131.jpg[/attachment:1tknbua5]

 

[Bama Rambler]

It's pretty hard to tell what it is but there are several possibilities.

I'd fix up a adapter and valve and quickly screw the cap out and screw the valve in and then run the pump and slowly crack the valve open and see whether it gushes water or sucks in air.

 

[msgtdan]

It's right above a return, I'm wondering if it's not a return to disturb the water so divers doing flips/twists can pickup the water surface.

 

[carolina pool]

It probably is an overflow that was set a little too low. Its possible that its a fitting that was set up for an pool cleaner.

 

[tkdtime]

Bama rambler, that sounds like a good idea. I'll give it a shot and see what I find out.

Carolina, is it common to have two lines set up for a pool cleaner in a pool? I have one return jet in between deep and shallow end that is set up for a polaris. Of course, this jet is clearly below the surface. The line pictured is always above the surface except when we get a ton of rain...