What is the Port for?

[Coach_1]

This port hole has a pretty powerful suction when I turn the valve to open. Is it for vacuuming and should it be on all the time?
i have 2 holes in my skimmer. Not sure if it's related to this.

 

[borjis]

Yep that's for a suction cleaner.

Leave it off unless a cleaner is hooked up to it.

 

[banditig]

Looks like a suction side vacuum port. Usually there is a flap to prevent somebody from getting trapped from suction. The extra hole in skimmer might be for if the vacuum hose gets clogged the pump still gets water. Leave it off without vacuum, yours is not safe especially for children.

 

[Coach_1]

I leave it off all the time as I did not know what it's for. Where can I get a cover for it?

 

[banditig]

https://www.bing.com/images/search?...890702A9A6A89F9EB49996F0FD99DAED1&FORM=IQFRBA