A few years ago I bought a used US military bivy bag (Gore-tex). Upon taking it in the bathtub, I found that a few small areas of repair were leaking (all on the underside of the bivy bag) The problem seems to be that the repaired areas' seams were leaking.

Is there any good way to repair this? I've heard that you can melt duct tape with an iron to make a good seal. Also, aren't there Gor-Tex patches I could throw over the repair patches? Would either of these methods make the bag waterproof again?

Thanks!