Broken pipe concrete floor help!!

[JohnD]

if there was the slightest trace of moisture in the pipe, it will not solder successfully.

It is harder to dry out a wet pipe than you think.

Try heating and taking it off and have a look.

It can be useful to tin the ends of the pipe before you solder it together - this gives a more reliable joint so is useful if you are very anxious to get it right - just clean the pipe end very thoroughly, flux, heat, touch with solder, wipe it round with a clean dry cotton rag while still hot and molten - you will find the solder sticks to the pipe not the rag.

Unless the solder is very thick, rough or lumpy, you will still be able to slide on a solder-ring fitting. If it is too thick, heat and wipe it again.

 

[Space cat]

Is it the lower of the two solder joints that's leaking? Of course it is. S*d's law says so! You'll have to pull it apart and try again like JohnD says. Or ----

Since you now have to dismantle a soldered joint, can you pull that piece of pipe out of the elbow below? It's much easier to make a good joint when the pipe is going downwards into the fitting. You can see what you're doing for a start. You can see the nice bright ring of solder that should appear in a well made joint and you can easily top it up with just a little more.

If it's the upper joint that's leaking you're in luck - as long as you can get all the water out. Start with a ring of flux around the existing joint and, when this melts and runs down into the joint, add more solder.

PS: There's something I forgot to mention, something that applies to all soldered joints. When it's all cooled down, CLEAN THE SURPLUS FLUX OFF! If you don't do this your pipe will soon be covered in horrible green streaks which will be much harder to remove than the fresh flux.