Using a union at a sillcock connection

Hi, I've been having a lot of problems getting my new sillcock to thread into the corresponding copper fitting (Sweated onto the supply pipe). I have had to re-do the supply several times because the chrome sillcock (1/2 mip) wants to eat the copper threads instead of going in peacefully.
Here is my idea for repair and rationale:
12" Sillcock 1/2 MIP, screwed to 1/2 FIP copper fitting, sweated to short copper pipe, sweated to male side of brass union Female side of brass union sweated to copper pipe sweated to supply tee
The sillcock is then joined to the supply at the union instead of at the copper fitting.
Rationale: - The male brass union will not eat the threads of the female brass union. - The brass union will not seize. Copper and chrome may seize, and in this design that is actually a benefit. The next guy can just turn the sillcock out, and with it comes the male half of the union (the part that is harder to damage). - The "Wiggle" from using the sillcock will be on the male side of the union, which is held rigid by the threads, so it shouldn't be possible to break the union seal by using the sillcock roughly.
Problems: - The sillcock is screwed in and the downspout must be vertically aligned for the freezey-proof to work. Conceivably, I can see a scenario where when on one turn when the downspout is aligned, the union has not yet sealed, but then the union becomes tightened before the sillcock is vertically aligned on the next turn. - Is a union going to be reusable in this situation? If the next guy's going to have to dig into the wall in any case, I'll just sweat the whole thing and be done with it.
Another idea was to sweat a 1/2 male fitting onto the supply pipe, and then attach a threaded copper coupler to the sillcock and use the copper coupler to connect to the male supply fitting. Copper on copper, so no seize and no eaten threads, but I don't even know if a threaded copper coupler exists, much less if it would be possible to seal the threads.
Ideas? Flames?
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wrote:

I don't understand why a sillcock will not screw into a copper pipe fitting. I've done many of them and they went on no problem. Have you replaced the fitting on the pipe which may have bad threads? It's also possible you have a sillcock with bad threads. Also, many sillcocks are made so they can either be screwed on or soldered on. So, you could solder one on. No reason you should have to use a union in this application, which is just asking for more potential problems.
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On Jun 27, 8:17 pm, snipped-for-privacy@optonline.net wrote:

I guess I don't understand that either. It's in the same hole the old one came out of so I would assume the hole is lined up. I can feel it catching but it cross-threads every time. I guess it could be bad threads, but I checked that the copper fitting will screw onto the sillcock by hand before installing it. After slightly cross-threading one and removing it, I was able to "fix" the copper threads by hand by screwing it onto the sillcock. It just won't go on that way when it's in the wall for some reason.
The sillcocks I got are from home improvement megastores. Two have flare ends and one has a MIP End. It seems like the one with the MIP end should be able to be soldered, but I was unable to get a 1/2 copper pipe into it.
The idea behind the union was to avoid the chrome seizing the copper, but from the sound of it that's not much of a problem? The one that came out had a copper supply fitting on a galvanic nipple that the sillcock was soldered to. The copper-galvanic joint was a molten mess.
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wrote:

The ones intended to be soldered or scerwed on that I have seen have male threads on the outside. Inside where the threads are, it's made to accept 1/2" copper pipe if you want to solder it in instead.
The advice to buy taps/dies is interesting, but I would think the tools would cost more than just buying a new sillcock and soldering on a new threaded adaptor.

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wrote:

<snip>
Find a real honest-to-gosh hardware store and buy a 1/2" NPT pipe tap and a 1/2" NPT pipe die. Clean the threads up with each of these tools and they will work perfectly. If you have trouble assembling at the installation site, then you have an alignment problem that you didn't notice at first. Correct that and you're good to go. HTH
joe
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On Wed, 27 Jun 2007 21:48:32 -0700, Joe wrote:

If this dude doesn't get this fixed ASAP I'm going to fly out to his home and fix it for him :)
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You were right, if you eyeballed into the hole everything looked like it lined up, but the hole through the stud was not square, and coupled with any displacement on the exterior wall it was enough to knock off the alignment by about 1/2 inch. I knocked another piece of brick out, put everything together again and I was done within the hour. No leaks!!
I am guessing this is also the reason why the old sillcock had a bent body, either the hole wasn't lined up to begin with and they beat it into place, or the exterior wall settling knocked the holes out of alignment and also gradually bent the sillcock as it settled.
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wrote:

so I now have a hole the size about 1/4 to 1/3 of a brick. I was thinking mortaring the hole is not a good idea if there is movement (since that's what probably caused my problem to begin with), but the idea of using Great stuff doesn't appeal to me because it's on the front of the house. Anything in between, that will let the sillcock shift in the hole over time but not look like a cheap fix?
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snipped-for-privacy@mail.win.org wrote:

Would a plumbing escutcheon cover it up? You could stick it to the brick with silicone adhesive:
http://www.plumbingsupply.com/escutch.html
They even have a "split" style if'n you don't want to unscrew the sillcock again.
Jeff
--
Jeffry Wisnia
(W1BSV + Brass Rat \'57 EE)
  Click to see the full signature.
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I didn't know they made split ones, that's cool. Then what I guess I'll do is mortar some the larger pieces of brick back in, leaving 1" all around the fixture for movement, use great stuff to fill the rest and sand it down, and then use the split style from your link to cover up the unsightly foam.
Excellent!
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GREAT STUFF IS FLAMMABLE
| > > wrote: | > | > >>I knocked another piece of brick out | > | > > so I now have a hole the size about 1/4 to 1/3 of a brick. I was | > > thinking mortaring the hole is not a good idea if there is movement | > > (since that's what probably caused my problem to begin with), but the | > > idea of using Great stuff doesn't appeal to me because it's on the | > > front of the house. Anything in between, that will let the sillcock | > > shift in the hole over time but not look like a cheap fix? | > | > Would a plumbing escutcheon cover it up? You could stick it to the brick | > with silicone adhesive: | > | > http://www.plumbingsupply.com/escutch.html | > | > They even have a "split" style if'n you don't want to unscrew the | > sillcock again. | > | > Jeff | > | > -- | > Jeffry Wisnia | > (W1BSV + Brass Rat '57 EE) | > The speed of light is 1.8*10^12 furlongs per fortnight. | | I didn't know they made split ones, that's cool. Then what I guess | I'll do is mortar some the larger pieces of brick back in, leaving 1" | all around the fixture for movement, use great stuff to fill the rest | and sand it down, and then use the split style from your link to cover | up the unsightly foam. | | Excellent! |
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