I bought a Polaris vacuum that connects to the return port of the pump. I can get the eyeball and its lock ring off with no problem, but I need to remove the insert and it won't budge. Is there any reason an installer might use glue? I'm afraid I'm going to destroy it if I force it too much. There's not much room to get a grip with pliers or a wrench and the only area exposed is the threads for the lock ring.