To help remove the water either use a shop vac with a jury rigged collection
of tubes taped together to get the size needed to fit over the copper
fittings, sometimes it can take 15 to 20 minutes to remove trickles of water
from a line, open a tap on a far away upper floor to aid in the airflow.
Sometimes a compressor can be used to blast the water from a higher level
down to where you are working.

The old lead/tin solder was much more forgiving in its use with a wide
temperature range where it was "mushy" and could be worked into a joint and
form a fillet. The lead free versions are difficult to get a tight joint.
Overheating can cause it all to flow right out a joint leaving pinholes.
Sometimes it pays to just add a little lead/tin solder over difficult lead
free joint just to build a fillet to plug those pesky pinholes.

"bdeditch" wrote in message
oups.com...
On Feb 2, 10:04 am, 46erjoe wrote:
In doing some recent plumbing work, I had to sweat a particularly
difficult and oddly shaped joint in the bathroom wall. I was surprised
when I turned on the water valve and it actually held! (I've never
been good at soldering copper tubing,)

Anyway, a week later, it developed a pinprick leak. In the past, I've
tried to re-sweat joints to no avail. But maybe I'm overlooking a
special technique or product.

Any help would be appreciated. I used tin/antimony solder. For now it
looks like I will have to disassemble the whole thing and that will be
a real mess because I will have to tear part of the wall apart.

Thanks.

Make sure there is NO water in the pipe. Sometimes it will sit right
at the joint after you take the connector off. The water will act like
a heat sink and make it a lot harder to sweat together. Find the
lowest point in the home to drain the water back.