I have some air on the suction side of my pump. It doesn't seem to be causing any trouble, but I want to be sure that I'm not missing something.
While the pump is running, there seems to always be a small air bubble at the top of the viewport - maybe a couple of tablespoons of air, if it makes sense to describe it that way.
But when the pump has been off for a while, this grows to the whole of the viewport dome, down to - but not below - the seal of the port. If I turn the pump on, this air is quickly sucked through the system and cleared, but if I wait another 10-15 seconds, a whole bunch of air gets sucked into the chamber, and after two or three seconds of churning, gets sucked through into the filter. Then I'm just left with those couple of tablespoons of air at the very top.
It's that big rush of air after 10-15 seconds that makes me wonder. I would expect that if there were a leak somewhere, the air would work its way up to the top of the system, which is what I think of as the manifold where the three returns (two at the bottom of the pool, plus the skimmer) have valves and then meet up, leading to the pump. But that's right next to the pump, so I don't get why (A) I'd be sucking through clear water at first, and then it would take 10-15 seconds of high-speed pumping for the air to get sucked in.