Can you patch over a patch on a vinyl liner or do you need to pull the old patch off?

The patch will hold better if you remove the existing patch. If you patch over the existing patch, make sure all the edges are sealed off.

If you are tired of replacing your vinyl liners, you might want to check out fiberglass as an option. A new fiberglass surface can be applied to your pool, and you will get a much longer life out of it. You can read more at: http://www.advancedpoolcoatings.com