Second pipe in skimmer?

[Northern cannonball]

I am wondering what this second pipe (on the right) in the skimmer is. It doesn't seem to do anything and appears to just trap dirt/sand etc.
The pipe on the left goes to the pump, any ideas what purpose the one on the right serves?

thanks!

 

[Jimrahbe]

N,

In the old days, the main drain was connected to the skimmer, normally at the hole closest to the pool water.

Now, most new pools, have the main drain run back to the equipment pad. When this is done, the extra hole in the skimmer is plugged.

Thanks,

Jim R.

 

[Northern cannonball]

Thanks Jim! Makes sense, even though I don't have a main drain.