Leaking connection to clawfoot tub! Help!

Hi all,
I am trying to stop a leak at the connection between the supply line and the threaded faucet shanks. My supply lines look more or less like this:
http://www.shop4classics.com/images/1xoffset.jpg coming out of the floor and at the tub end having a nut and a cone shaped fitting on the end. The nut is supposed to screw onto the threaded faucet shanks. When I do this, WITH or WITHOUT Teflon tape wrapped around the faucet shanks, water leaks around the nut (in front of the nut over the shank and behind the nut on the supply). I have tried torqing the night pretty hard with a 12" crescent wrench with no luck and a fear that I'm going to break something.
Any suggestions? Is there something else I should be putting on the threads to stop the leak?
TIA,
Bart
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BRN wrote:

The threads do not seal *anything*.
The cone on the supply does all the sealing against the "inner cone" on the faucet inlet.
Once the cone has been deformed from previous connecting it may no longer seal properly again.
You could try a thin film of silicone caulk on the cone, or even Loctite. Let harden before turning water back on.
If there is any risk of breaking something by replacing the supply line, I'd opt for the caulk first.,
Jim
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BRN wrote:

Sounds like the kind of joint where the seal is the cone and the flared pipe (or a cone on the pipe and a female fitting on the tub/faucet), the threads are just there to hold it together. Take it apart and inspect the cone and the inside of the flare for damage or scratches a little emery cloth might be all that is needed. You might try a little bit of pipe dope on the threads to stop the leak but I doubt it. You may need to get a reamer at the plumbing store to resurface the fittings. You are right not to overtighten this joint, moderate pressure should seal it.
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Thanks all. That makes sense that it is the fitting that's gone bad and not a problem with the threads. I'll try some silicone and if that doesn't work, a new fitting. B

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