Well the leak guy came out and found our leak in about the first 10 minutes: where one return line comes in, the nozzle fitting appears to have not been attached properly (bad glue job maybe?), or may have pulled loose with settling and shifting... and someone in the past seems to have "repaired" it with Fix-It Stick or some sort of other hardening material.. and now that material is cracked or loose or in some other way allowing a slight trickle escape.
Obviously to re-fit it properly means peeling the liner back, digging down to the pipes, etc. That can be something left to the pool pros for the off-season.
Meanwhile, I need to find some way to keep it going through the summer without needing to top the pool up every day. I'm thinking to chip out the old stuff and use a bead of Sikabond (immersible polyurethane), which is super sticky and stays flexible... only catch is, it's supposed to have 4-7 days to cure fully, and with the hot weather, I really don't want to be without the pool for that long.
Can anyone offer any other tips for a quick, temporary patch? I haven't chipped the old stuff out yet to confirm what kind of gap there is....