Copper must be cleaned to remove surface contamination prior to soldering.
There are a number of ways to do this. You can use fine grit sandpaper, emory cloth, or a tool
designed for the purpose. Whatever method you choose, the mating surfaces of the parts to be
connected must be bright and shiny. Otherwise, solder will not bond
and you will end up with a leaking connection.
Here are the steps to a successful sweat solder job:
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Measure, cut, and
dry-fit all parts. Be sure you have cut pipes to the correct length.
When fitted together, about 3/8 additional inch will be needed on each
side of an assembled joint to account for the connector.
-
Clean the mating
surfaces of parts to be joined - outside surface of pipe, inside
surface of connector. Use one of the cleaning methods mentioned
earlier, and don’t touch the parts with your fingers after cleaning.
This step must be done properly. Any contamination on the surfaces to
be joined will prevent the solder from bonding.
-
Apply a light coating
of flux to the outside mating surfaces of pipes and inside of
connectors. Be sure to get an even film all the way around. Use a
small flux brush for this task. The purpose of the flux is to remove
any unseen surface oxidation, etch the copper, and guard against
oxidation when the parts are heated.
-
Assemble the parts to
be joined. Support the pieces on something that will not burn or be
damaged by heat. If working in an enclosed space, protect surrounding
areas with a flame blocking material and keep a fire extinguisher
handy. Be mindful of items that can be damaged or destroyed during the
heating process. This includes you! Don’t burn yourself on the hot
parts, and be sure to protect your eyes. If working overhead, do not
position yourself directly below the parts to be joined.
-
Pull about 12 inches of
solder from the roll. Begin soldering by applying heat - first to the
outside of the connector where the pipe is inserted, then back and
forth across connector and pipe. Keep heating until the flux begins to
bubble and smoke slightly. Don’t overheat or the solder will not bond.
-
Touch the tip of the
solder to the point where the pipe enters the connector. If at the
correct temperature, the solder will instantly melt and flow into the
joint. Maintain contact just long enough for the solder to appear all
around the fitting. Don’t use too much because the excess will flow
inside the joint and possibly form a blockage.
-
Allow the soldered
joint to cool by itself. Don’t move it around while cooling, and don’t
use water or anything else in an attempt to speed-up the cooling
process. If the solder is cooled too fast, it will become brittle and
probably fail at some point.
Valves require special treatment when soldering, and there are two
commonly used approaches. The first is to remove the valve stem, with
its rubber washer, from the valve body and attach the pipe by
soldering. Once the valve has cooled, reinstall the valve stem. Do not
try to solder the valve with the stem in place as the heat from
soldering will melt the washer and render the valve ineffective.
The second approach involves using a threaded valve and attaching
threaded couplings to the ends of copper pipe. After the pipe and
couplings cool, thread them into both sides of the valve.
That’s it! There is nothing difficult or intimidating about sweat
soldering. A few specialized tools will make the work go easier and
faster. While it takes a little practice, it is well within the reach
of the do-it-yourselfer.