Since solder joints involve the use of a blowtorch, make adequate provision for the prevention of fire. Never allow the flame to point towards combustible items. Be extra vigilant when working in confined areas. Use a protective mat behind the area being heated to reduce the spread of heat.
Ban on lead solder
From 1987, the Water Supply Byelaws outlawed the use of lead based solders for domestic hot and cold water systems. This was incorporated into the Water Fittings Regulations. The potential for health problems and the dangers of lead poisoning gave rise to this legislation. Under the Regulations, solder containing lead may be used only on non-drinking water where the water is not required to be wholesome such as closed circuit central heating systems (Source: Water Regulations Advisory Service).
There are two types available. Standard end feed and the integral solder type.
Preparing the joint
Cut and test assemble the piece first. Once this has been done, soldering of the joint may be started. But, remember that both ends of a joint will need to be soldered at the same time. If you try to heat the second end of the joint, after the first has already been completed, the heat will re melt the solder on the first, causing the joint to fail.
All parts of the copper to be soldered need to be completely clean to ensure a good bond. Use wire wool to remove dirt and grease and continue a little to remove the oxidation on the pipe. You should now have shiny ‘new penny’ looking ends.
Apply some flux to each surface of the joint. This is a paste which prevents further oxidation and assists the flow of solder. Application is easiest using a small craft brush – one of the really cheap ones since it will be useless for any other purpose afterwards.
Assemble the solder joint
Reassemble the joint giving each part a twist back and forth to spread the flux.
Now line up the assembly so that every component is in the right place. The shape and direction of the pipe must be as you originally intended since no adjustment will be possible after the connection has been completed. Obviously, with a straight joint there will be no problem but, when assembling bends and junctions, it is easy to do a beautiful job of the joint only to find the direction of the pipe has moved a little out of line.
End feed solder joints
You will require a reel of suitable solder and should unroll a little so that it can be applied without getting your hands too close to the heat.
Light the blowtorch and allow it to burn for a minute or two. This allows the nozzle to heat up, which seems to reduce the chance of the flame flaring up when the torch is tilted.
Gently and evenly apply heat to the whole joint. As soon as the flux begins to bubble, remove the heat source and touch the solder at several points around the ends of the joint. Capillary action will draw the solder in between the pipe and the joint. Apply enough solder so that you see a complete ring of it around the mouth of the fitting. Allow the joint to cool.
Integral solder joints
These are worked in a very similar fashion except that the solder is already in place and as soon as sufficient heat has been applied, it will be drawn from its groove into the narrow gap between fitting and pipe.
As before, remember to apply heat gently and evenly. As soon as a ring of solder appears, remove the heat source. Continued application of heat can cause the solder to drain out of the joint altogether.
Allow to cool.
Leaking soldered joints
If you are unlucky enough to find that a solder joint leaks when you switch the water back on, all is not lost. The chances are pretty low unless there was a residue of water in the pipe which will have stopped the solder adhering.
Switch off the water and drain the section of pipe. Apply a little heat to the join to make quite sure it is dry again. Heat up the joint again and apply a little solder from the end of the reel to the mouth of the leaking part. This will work with both types of soldered connection.
If you a really unlucky and the joint still leaks, You will need to drain down again and remove the joint. Heat it up and dismantle the join whilst wearing some form of heatproof gloves. You now have two options. Clean the pipe thoroughly and use a new fitting or, if your feeling totally disheartened, take the easy route and fit a compression joint here instead!
Note that all pipework should be adequately supported with pipe clips.