I put in some of those cheap home depot couplers as a short term solution until i got some silicone,a nd i was actually very surprised at how well they've lasted. I haven't bothered replacing them since. They're ugly, and they deform, and they stretch when yo hit boost, but they work, and they're cheap. I don't know why yours were melting, unless they were on your turbo outlet, and youre pusing a small turbo way out of its efficiency range.

Anyways... silicone is better (my silicone couplers are on the way), but the plumbing stuff does work.