I've got a leaky hot-water pipe joint that feeds the dishwasher.
Leaks from the tee where the shut-off valve is, under the sink. Is
this a good choice for my first-ever DIY plumbing attempt? I'm plenty
handy with wood and electrical, but haven't attempted plumbing. I've
got the flux/solder/etc, and have watched a zillion shows and read a
zillion books, Whaddayathink? Can I just resolder the thing, or
does it have to come apart and go back together again?
Sure! It's cramped under sinks and a little hard to work under there, but
why not? You might look into compression fitting the new shut off if the
pipe is clean and undamaged. Less dangerous than sweating a new fitting
in - no flames.
For the record, my first plumbing project - besides replacing the fill valve
in the toilet - was replacing a water heater. No different than eating an
elephant: you do it one bite at a time.
To give your question a direct answer. If it's leaking from a soldered
joint between copper piping and a fitting, don't try and fix it by just
reheating the joint or piling solder on the outside.
Far and away the principle reason soldered plumbing joints leak is that
the installer either didn't properly clean and flux both the pipe and the
inside of the fitting before heating them and applying solder, or he/she
didn't heat the joint area enough so that it reached soldering
temperatures all the way away around the fitting. You can't clean the
mating surfaces while the pipe and fitting are still together, and no
amount of heating will make solder wet onto dirty surfaces.
If you're going to fix the leak by resoldering, you will have to
disassemble things to accomplish the job.
Soldering copper plumbing is almost a no-brainer, providing you do three
1. The srfaces which will be wet with solder have to be clean and bright.
This is can be accomplished with abrasive cloth or wire brushing, but it
must be complete with no traces of "brown" (oxidized copper) left.
2. Flux has to be applied to all the surfaces to be joined.
3. Enough heat has to be applied with a torch all around the fitting so
that wire solder will melt immediately when touched to the juncture at
the end of the fitting and the pipe, immediately after the torch flame is
moved away. When done properly, the solder will melt, get sucked into the
joint and "run" all around the fitting without further effort. (Don't
bump or move the pipe until you've waited long enough for the solder to
In tight quarters you can shield walls or other things you don't want
scorched with two or three folded layers of kitchen aluminum foil. It'll
reflect the heat away fine, as long as you don't play the torch directly
That being said, there's nothing wrong with using compression fittings
for a repair job like the one you're describing. You might want to aquire
a pipe cutter if you don't already have one. They make nice little
cutters for close quarter work which will swing around a pipe that's only
an inch or so away from a wall. It's much easier to use one of those than
trying to bull your way through copper with a hacksaw while cramped under
Jeff Wisnia (W1BSV + Brass Rat '57 EE)
"If you can keep smiling when things go wrong, you've thought of someone
to place the blame on."
A word of advice - you will not be able to melt the solder unless you get
all of the water out of the pipe. This can be difficult with a dishwasher.
In your case, opening the kitchen taps and/or removing the top of the
shut-off valve may do the job .
The proper way to do this job would be to turn the water off at the main
shut-off (basement?), open the kitchen taps and a tap somewhere lower than
the dishwasher (basement?), remove the top of the shut-off valve if it is a
tap-washer style so you don't melt the rubber washer and to let air into the
pipe (or disconnect it at the union if it has one), heat and pull the leaky
joint apart, clean the pipes (by heating them and wiping with a rag),
replace any removed fittings with new ones (they are cheap and difficult to
Be sure to clean all surfaces to be soldered with sand paper and use proper
(lead-free) solder and flux.
Plumbing is fairly easy so you should have no difficulties if you are
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