Plumbing, compression fittings question

Any trick to keeping compression fittings from weeping?
I'm replacing the water supply-line valves in my bathroom (hot and cold to the basin, cold to the toilet). The old ones were 38 years old and I wanted to upgrade to the new 1/4 turn ballcock design. This is part of a total bath remodel.
The supply lines are 1/2 OD copper pipe and the valves attach to the copper pipes with a compression fitting (brass sleeve between the valve body and the compression nut).
Seemed straightforward, after removing the old valves I made sure the supply lines were not out of round and were not galled. The ends of the pipes were cut at 90 degrees as they should have been. I used fine steel wool to remove any surface corrosion and to leave a smooth surface.
Wiped everything down well, installed the valves hand-tight (being careful to not over-tighten) and turned the water back on.
Two out of the three valves weeped water around the compression fitting, I could feel moisture where the pipe entered the compression nut. Not enough to drip, but not a perfect seal. Tightened a little more by hand, rechecked, and they were still weeping.
I finally removed all the valves, put on new compression sleeves, but this time I smeared a thin coating of pipe thread compound (Harvey's TFE paste) around the pipe before I put the compression sleeves on. Tightened everything hand-tight as before, turned the water on, and no more weeping. Dry as a bone.
Question: is it common for new compression fittings on old pipes to weep? My solution worked but is there something else I should have done instead What would a "regular" plumber have done? I might need to go through this all again in another bath.
Thanks for your help.
- Spellcheck
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Spellcheck wrote:

Personally, I'm in favor of the sealant paste. Not only seals but reduces friction by a lot as you're tightening. You *shouldn't* need sealant when everything is perfect but it's a good backstop.
Jim
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Thanks, Jim, for your pertinent reply.
- Spellcheck
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Spellcheck wrote:

will not leak.. remember its a compression fittng... you have to compress with it and you not doing it with your hand... the sealant you put on might not let it leak now, but its still not compressed and might leak sometime down the line when no one is home to turn it off??????
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Had new valves put in along with some new 1/2" supply lines during some remodeling. Valves were soldered on the supply lines. According to the plumber, this is the way that all new installations are put in--no more threaded or compression fittings. MLD

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Couple of things.....
Like other poster, I think the more common way to mount the valves would be to solder on a pipe/solder to male pipe thread adapter, tape and screw on the valve. I don't recall seeing ball valves with 1/2 inch compression fittings made in, only either female pipe threads or solder fittings. So I'm guessing you installed a compression fitting into the valve. Seems like an unusual choice.
Compression fittings DO NOT SEAL BY THE THREADS. The threads are used to swage a ferrule onto the pipe and then to hole the ferrule tightly to the female side of the fitting. If your first ferrules were removable, as implied in your post, then the swaging never took place. Done correctly, these pieces are virtually welded in place, and would be sawed off if neccesary. It's like the pipe grew a 'ball' on the end. The best are 2 piece ones, were 1 has a taper to slide under the other, and the swaging takes a minimum # of turns of the wrench. The 'ball' is pressed into a mating maching in the fitting, and forms a seal. Likely, dope allowed you turn the wrenches easier, and you may have swaged the ferrule to the pipe. Other wise, you have a low quality joint sealed only by the dope.
Hope this helps....

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I agree with the sweated connections to replace your compression fittings. Everything in my house is sweated and it was done by professionals, not me. I think you would be happier with them.
I've noticed that most of the compression fittings in the stores use a rubber washer instead of a ferrule and you only have to hand tighten them. I'm not sure why both are called compression, but I like them.
PJ
On Fri, 19 Dec 2003 17:32:10 GMT, "Spellcheck"

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Maybe you used too much elbow grease with the steel wool. I find that the pipe surface needs to be in virgin condition in order to seal properly.
Richard

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Real plumbers use wrenches to tighten compression fittings.
Excellent plumbers use sweat solder fittings.
--
Christopher A. Young
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And plumbers that know better use neither now. Get with the program Chris....you really need to get up to date...
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