If the pvc is threaded, you could try teflon tape. Otherwise, you'll probably need to stick with silicon until you change systems and can fix it properly. Make sure the bucket is well drained before doing this. remove the old stuff and add new. give the silicon time to cure before adding more water. the water pressure is the absolute worst for forcing little holes through wet silicon.
Another alternative, if its not to much leaking, is to elevate the pot and simply catch the leakage and return to the rez. One caveat, if its outdoors, is yellow jackets will love the easy source of water.

With no picture can't give much help and not knowing how things are configured can't even guess.
It sounds to me like you are trying to salvage a bad idea and don't want to disturb your plants.
We have used plastic to fashion temporary buckets,Good luck.
"Doing 10 with no Chance of Parole"

Personally, after trying to fight leaks for nearly a month and never really solving the problem completely, I would go back to square one. Take a couple of hours. Put your plants in a bucket of water - they will survive. Get grommets for your buckets and after they are in and the pipe installed, use silicone around the edges. Let the system sit overnight, then reload everything.

You will be glad you did!

Mike

I could be wrong, but I seem to recall a while back someone mentioned that there was a product they use that will dry and cure even when wet. I forget what it was called, or even what thread it was mentioned in (otherwise I would look for it), but hopefully someone will remember and chime in. Though I would agree fixing it right (even if disturbing the plants) would probably be the best way to go. I have had to do that a couple of times myself. Now I try to foresee any potential problems, and fix them before I put the plants in the system (living and learning from my mistakes).

But if I have the problem to deal with, I come up a plan of attack, and figure out the quickest way to accomplish it. That could be either building new more durable buckets that wont leak (after assessing what went wrong, and why the old ones leaked), or rebuilding the old ones to be more durable and not leak. If using new buckets, it will be easier to just swap out the old ones for the new ones. If rebuilding the old ones, you will probably need a temporary place to keep the plants alive while you are working on the buckets. Either way I always make sure I have everything I could possibly need ready, and if possible I like to have another person there to help just in case I need an extra set of hands.

1 Picture > 1000 words. If silicone didn't work, it wasn't applied correctly. Not trying to be rude, but silicone works every time it is applied right. You MUST follow directions. You might get lucky taking shortcuts, but you guarantee success doing it right. Take the advice of wordwiz. He's right. I've screwed up enough and fixed enough screw ups to know that sugar coating it will only hurt you, so there you go.