Plumbing question on opening

[doncaruana]

Doing my first opening myself here and had a head scratcher. I took the plug out of one of my returns (the jets in the pool - that's a return, right?) and on the first one there was a major vacuum and a bunch of water immediately started getting sucked in., like the pump was running backwards (haven't even started it yet).

When I did the other one I got a major air bubble.

As a side note, I get that kind of behavior regularly in the morning startup.

Does that indicate there's maybe a leak in the second line somewhere? And, if so, how the heck would I find and fix it?

 

[JasonLion]

No, that doesn't really tell you anything. The plumbing was sealed up over the winter, and temperature changes could easily have lowered the pressure in the plumbing, causing some suction when first opened. Air bubbles are also very common when first opening, as the pipes will start full of air.