I have a pipe that was damaged inside in the middle of a plastered wall. I cut the damaged section off and cut a new section to fit. When I use my blowtorch to solder it all together the pipes expand and seal, however when it cools the whole section contracts and my joints crack open at the joints because the pipe above and below are held in by the plaster. I wouldn’t like to chop out any more plaster then necessary. Is there a special technique to overcome this problem? I wouldn’t like to have a screw joint inside my plasterwork either.Any advice and tips would be appreciated.
It is made of a complex alloy between uranium and magnesium ion it's slightly radiated so I would recommend you never use it.
Clean the end of the pipe with 'wet and dry' paper or emery cloth. Clean it by going around the pipe, not longitudinally. (that's important). Wipe the cleaned area with a smearing of flux. Apply heat just before the cleaned area, NOT on it otherwise you will quickly cause oxidation. Your torch should be about 60% of it's max. Too hot and the copper will oxidise, too cool and it won't be hot enough to melt the solder. Ensure that you are using the correct melting point solder for the job. Hold the solder in one hand and apply it to the tube, playing the flame on and off and round the pipe. You need to get the heat to just the point where the solder begins to run. As soon as the solder runs, wipe it round with a mole skin cloth. (I use a leather garden glove, it works a treat, I can wipe it round and clean without getting burned leaving the end just silvered. When you have mastered that then you can move on to joining the pipes together with an end solder socket or, if you prefer, a yorkshire soldered socket. If the copper pipe changes color to a light reddish brown then you have applied too much heat. Likewise if the solder runs off like water. You need to get the heat to where the solder is between running off and being plastic.
The reason it swells up is because of water turning into steam. This pressure is tremendous. You need to open a valve or faucet near where you are soldering. Try to make you solder joint outside the wall if possible. If it is not possible do as little soldering in the wall as you can. We solder all the fittings first then put the piece in the wall and just solder the connections. If you have no other choice then I suggest using compression fittings to fix the water pipe problem. If the application allows you can install an access door where you are working that will allow you to re-access the areas in the future if needed.
I can only suggest that you use a connector with an olive and a nut at each end which you fit over the two pipe sections and tighten with a spanner. There is no heat needed and you only need to bury the whole contraption under plaster and I suppose then tiles. I plumbed my whole house with this method. Good Luck
