There's a right way to solder copper pipe—and a wrong way. Learn the difference so that your next bathroom or kitchen plumbing project is successful and trouble-free.
By the DIY experts of The Family Handyman Magazine:October 2007
wring out a 2-in.-wide strip of cloth and wrap
it around the fitting you want to protect.
The wet rag absorbs the heat and prevents the
solder in the existing joint from melting.
Lead-free solder melts at a higher
temperature than the now-banned
lead-based solder. MAPP gas torches
burn hotter than propane, making
them a better choice for modern
solder. Five to 10 seconds of
heating with a MAPP gas torch
is all that's required before you
can feed solder into most
1/2- to 3/4-in. pipes and
fittings. Be careful, though.
It's easier to overheat a
joint with MAPP gas.
If the flux turns black
and the solder won't
flow into the fitting,
the joint is
Don't solder close to wood or other
flammable material without protecting it from the
flame-retardant blankets are available
at hardware stores
and home centers.
on to insulate
material and help
prevent fires. In a
pinch you could
use a piece of sheet
Wetting the area
around the soldering
job with a spray
bottle of water also
helps prevent fires.
Keep a fire extinguisher
handy as a
Don't reuse old fittings. Recycle them
instead. It's time consuming and difficult to take apart
and clean old fittings. And there's a good chance they'll leak. Buy new fittings instead. You'll get better
results in less time.
Don't feed too much
solder into the joint. It's tempting
to melt a few inches of solder into a
joint as extra insurance against leaking.
But excess solder can puddle
inside pipes, restricting water flow,
and can form small balls that break
loose and damage faucet valves. Use about 1/2 in. of solder for 1/2-in. pipe
and 3/4 in. for 3/4-in. pipe. Here's a tip. Bend the end of
the solder at a right angle, leaving a few inches below the
bend. The bend makes it easier to gauge how much solder
Solder drips can clog the threads, making it
difficult to get a good seal when you
screw on the matching part.
If the threaded
fitting is positioned so that solder
will run down onto the threads, solder the
pipe and fitting at a workbench instead so you can keep
the fitting pointed up.
If you have to solder a
threaded fitting where
the solder will flow
onto the threads, make
sure to wipe excess
flux from around the
joint after you assemble
the pipe and fitting.
Extra flux can
run down onto the
threads, causing the
solder to follow it.
Tinning flux works just like
standard flux but contains a
bit of silver
melts when heat is
applied. The resulting thin
layer of solder helps ensure a leakproof
joint. Tinning flux is available at
most hardware stores and home centers and
only costs a little more than standard flux.
Don't try to solder pipes with water in
them. When you're repairing or tying in to existing copper
pipes, it's common to find a small amount of water in
them even after you close the valve and drain the pipes.
Soldering a joint in pipes that contain even tiny amounts
of water is nearly impossible. Most of the heat from the
torch goes into turning the water to steam, so the copper
won't get hot enough to melt the solder. Stop the trickle of water with a pipe plug.
Push the plug into the pipe with the applicator tube provided.
When you're done soldering, dissolve the plug by
holding the torch under the spot where the plug is. Plugs for 1/2-in. or 3/4-in. pipe are sold at home centers and hardware stores.
An old trick was to stuff a wad of soft white
bread into the pipe to stop the trickle of
water temporarily. This works but
you run the risk of clogging
aerators and valves with
Cut, flux and assemble a
section of pipes and solder them all at
once. Soldering one joint at a time is inefficient.
Use pipe straps to support the pipes
if necessary. Be careful to clean and flux the
end of every pipe and the inside of the fittings
before assembling them. Then just
before you start soldering, press the pipes
firmly into the fittings to make sure they're
fully seated. Start soldering at one end of
the assembly and move methodically from
one joint to the next.
Have the necessary tools for this DIY project lined up before you start—you’ll save time and frustration.
You'll also need a flux brush, plumber's sandpaper and wire brushes for cleaning pipes, and a flame protector.
Avoid last-minute shopping trips by having all your materials ready ahead of time. Here's a list.
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