Inground piping

can someone explain the piping on my pool? I have a 16x32 inground vinyl .1 deep end skimmer .  3 returns. 4 deck jets . No floor drain. There’s 1 pipe going into pump and 3 going out. Probably 1 for returns and 1 for deck jets. What’s the 3rd?

Thank you for contacting Inyo. It’s possible that the 3rd line could be going to a line intended for a pressure cleaner.

Is there a way to put a picture on here?

You can post a picture but it will still be a guessing game for us since we’re not able to test each line.