"Proctologically Violated©®" wrote in message
...

I have previously screwed up sweating ball valves, and frankly
don't see how the teflon seals withstand the heat, even with
"good technique", which mine most likely is not, given the rare
plumbing that I do.

The melting point of Teflon ranges from 500 deg F (Teflon FEP) to 621 deg F
(Teflon PTFE). From a site on the properties of Teflon:

"The melting point of Teflon PTFE is one of the highest in organic polymer
chemistry. Due to the strength of the carbon-fluorine and carbon-carbon
single bonds, appreciable thermal energy must be sorbed by the polymers
before thermal degradation."

The melting point of typical lead-free solder ranges from 450 - 495 deg F.
Therefore, if you apply the heat correctly, your solder will melt before the
Teflon is damaged.


I am not a professional plumber. But I've done a lot of plumbing repairs and
upgrades. This is what I do:

1. Ensure that your parts are CLEAN! Use those special wire pipe cleaners to
make sure you have nice shiny copper at both mating areas of the joint.

2. Apply a thin coat of water-soluble flux to both mating areas.

3. Fit the parts together. Make sure your geometry is correct.

4. Open the valve you are going to sweat so that hot air/steam can escape.

5. I like to wrap a wet (but not dripping) towel around the valve mechanism.
Probably not necessasary, but it also helps you avoid charring the rubber
coated handle if you accidentally pass your flame over it. Just be sure to
keep the towel off/away from the joint you are sweating, otherwise you'll
never get it hot enough.

6. Sweat the joint with your torch. Use a high heat flame. (If too low a
flame, you will just dump heat into your pipes over a long period of time
without the joint ever getting hot enough to melt the solder. What you want
is high localized heat at the joint, before the rest of your pipe/valve has
a chance to get really hot.) Focus 90% of your heat on the pipe leading into
the valve.

7. As you're heating the joint, occassionally pull the flame away and touch
the tip of your (lead-free) solder to the edge of the joint. If the temp is
right, the solder will melt and instantly wick into the joint. If it sticks
or doesn't immediately start to flow, it's not hot enough: take away the
solder and apply more heat from the torch.

8 It doesn't take much solder to make a good connection. Avoid the
temptation to flood the joint with solder. You should just see a tiny silver
fillet around the circumference of the joint.

9. Allow the joint to cool and solidify before attempting to move or do
other work on the pipe.

10. If you have difficulty getting the solder to flow or if you have drips
and/or blobs of solder, there are four possible culprits: joint not clean,
not enough flux, not enough heat, or too much solder.



So what I do is buy threaded ball valves, and separately sweat a
suitable length of copper pipe to copper adapters, screw those in
to the threaded valves, and continue sweating some safe
"thermal distance" from sed ball valve.
Sometimes I'll even use a union, depending...

In general, I sort of mix threaded w/ copper, like for caps:
Instead of sweating a cap to a tee, I'll first sweat an adapter,
and then screw on a threaded cap--makes subsequent connections
easier, I think.

Each threaded adapter you place in your system increases the cost,
complexity, time to do the job, and the possibility of leaking. If you
practice and learn to solder correctly, you can save a lot (in terms of
money, time, and headache) by eliminating these extra joints.


I always found sweating previously-wet copper
"in line" a real pita.

This really isn't that difficult. First, make sure your joints are very
clean. Water deposits, scale, old flux, and old oxidised solder must be
cleaned away. You should have a bight shiny silver joint. (It's silver from
the *now clean* old solder. It is neither neccessary nor desirable to remove
all the old solder down to the base copper pipe. The old solder provides a
pre-tinned joint for you.) Next, make sure the joint is bone dry. You may
have to drain all the upstream and/or downstream pipes to make sure no water
trickles into your joint as you're trying to solder it (sometimes it helps
to blow air into the pipes). Plumbing supply shops sell dissolvable capsules
that you can press into the pipe to stop any water from getting into your
joint as you're soldering, but an old plumber's trick is to use the soft
white center from a piece of bread to do the same thing. Frankly, I've never
needed to do either: i've just made sure the pipes are well-drained and that
the pipe near my joint is wiped dry.


Regards,
Michael