Wicked leaks

Yesterday I tried to fix a succession of leaks on this bit of pipe work. Trying to spot a dry joint is almost impossible when you can’t get your head around the back. So I partly filled and emptied the system three times cos you can’t solder a pipe full of water. Which is a pain in the ar5e.
Then today there was a tiny puddle under the same pipe.
But luckily it was a leaking union joint easily cured with a spanner.