Main Drain + Skimmer -> 4 way valve (Main Drain, Skimmer, 1/2 or off) -> pump -> filter -> swg -> 2 returns
Last week I noticed that I was getting air bubbles out of one of my return jets. Don't know exactly when it started but I suspect that it was soon after I cleaned out the pump skimmer. I checked with the 4 way valve on main drain only then skimmer only... bubbles in either case.
This past weekend I checked all the plumbing and found no noticeable leaks on the inlet side of the pump (turn pump off and watch for any water coming out of the connections/unions.... also the shaving cream trick). I took everything apart just in case and re-assembled with new lube + thread sealant. Checked again and no leaks.
So my conclusion is that I have either a leak in both the main drain and the skimmer lines or a leak in the pump/pump housing (likely the case). It's been a couple of years since I replaced the rubber gasket on the pump skimmer cover (Hayward Super Pump, rectangular gasket). The gasket doesn't look bad but there are no other obvious places for air to get in.
The gasket is simple enough to replace but is there anywhere else I should look at?
Also... while I was at the pool store I saw that the gasket is also sold as a part of a rebuild kit which includes the Housing Gasket, Diffuser Gasket, Lid Gasket and the Motor Seal. I've never rebuilt the pump before... Is this something I need to do regularly?