Red Sea Reefer 450 plumbing issues

[optimisticdingo]

Hello all! I recently purchased a used Red Sea Reefer 450 and have started to uncover some plumbing issues. The drains and return have leaks and I'm having a hard time repairing them. The previous owner must have known about these leaks in the past as they used silicone around the O Rings making the pipes virtually impossible to get loose. Do you guys have any suggestions as to how to get the pipes loose so I can replace the O Rings? I'm not opposed to completely re plumbing the overflow if needed. I just want the thing to work.

I'll attach a picture of where the leak is to show you all the problem.

 

[lapin]

They make chemical silicone solvents (eaters). You could try one of those. Not sure about how what it will do to your bulkheads.
You can get a Liftoff product that is like a penetrating oil to break the bond between the silicone and the bulkhead threads and tank