Pool solar panels are repairable, but the method matters because the panels flex and heat up every day, and that movement kills patches that would work fine on rigid pipe.

For the hard rubber collector, the plugs can work if the hole is small, but only if the area is clean and bone dry when you set them. Epoxy over the plug is worth trying as a backup, but be ready for it to crack loose when the panel gets hot and expands. The longer lasting fix is a repair kit made for your collector brand, with patches and primer meant for that rubber, or cutting out the damaged tube and bridging it with a proper splice kit.

For the white PVC coupling that still leaks, do not use silicone. It will not hold pressure for long. A leaking solvent weld joint needs to be cut out and redone. Shut off the solar loop, let the pipe dry completely, then prime and solvent weld a fresh coupling. While it cures, keep the line dry.

The leak under the collector at the connecting point is often a loose barb fitting or a worn header gasket. Shut the solar loop off, relieve the pressure, pull the fitting, and reseat or replace it.

Test each repair by running only the solar loop and watching the spots for a full heat cycle before you walk away.

John Anthony, ProLine Leak Fix Pros, Lynnwood WA
https://prolineleakfixpros.com