My question is I have been using 15mm solder rings to fabricate a central heating run. I think my last joint was not mated fully into the elbow joint. I was joining the other end and it melted the solder to the pipe. I now know I should have wrapped it with a wet rag or just been more careful.

From my measurements it is about half way in so maybe 7mm short. The joint is good as far as I can see but will the pipe not being fully inserted into the elbow cause a problem?
I will have to re-do the whole lot otherwise I guess.
I have not connected it up to the central heating yet.
Thanks in advance, Stewart