What is this connector?

[TimInMass]

I'm new to in-ground pool ownership, I'm not sure what this connection is used for. It appears to be sealed off with some rubber membrane material. I took off the cover ring but the rubber membrane material appears to be sealed and doesn't come off.

Any idea what this is supposed to be used for? Thanks in advance.
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[JasonLion]

That is a fitting put in just in case you want to run a pressure side cleaner in the future. I suspect there is a pipe that runs from there to the equipment pad that isn't hooked up to anything on the other end. They never cut out the liner to reduce the possibility of leaks.

 

[TimInMass]

That makes a lot of sense because there is a pipe going to a booster pump, but the booster pump doesn't look like it works, it's not fully hooked up and only the pipe going into the ground is connected to the booster pump the other end of the booster pump has a fitting blocking it off - all the other pipes are connected.

Thanks for your quick response! I've learned a lot from this web site.