compression nut leaking on cold water to sink

I have a shutoff valve attached to the cold water (copper) line running up to vanity sink. Its connected via compression nut. I'm wondering if i've compressed too far? or not far enough? I have a steady leak of water droplets out of there, i'd say 5 drops per min? do i need to keep tightening or have i "ruined" the connection and need to re-cut the copper and reinstall a new compression valve?

 

I would shut the water off, remove the valve and see if you have dimpled the copper where the ferrule is. From there, if it isn't, then I would redope and reinstall, snug it tight. If the leak persists, slightly turn it with a wrench until it stops. I rarely have problems with compression valves leaking; if I do then the quick turn of the wrench usually takes care of the problem.

 

From what I've read from compression fitting manufacturers, they say no tape or dope, and not to overtighten them; the prime cause of failure.

Gary
Quality Water Associates

 

That's what usually kills me... overtightening them.

Just installed 3 of them yesterday... After cutting the caps off the pipes, I cleaned them thoroughly with emery cloth. Then I put the fittings on, tightening them, I thought, just enough to keep them from flying off when I turned the water back on... I thought I'd let them drip from a loose connection, then slowly tighten them till they were dry. I'll be darned if they didn't work perfectly from the start... 36 hours later.... still good.

 

yup, that's the trick for me... only took once (in early apprentice years) to overtighten one. Full blown pressure charging out of a 1/2" pipe is not fun!!! I immediately adopted the practice of under-tightening, and snugging up the nut once the pressure was on and the water was running to the fixture. For old ones that seem to suddenly spring dribbles now, I give them the tiniest of cranks you could possibly imagine with the water flowing, and it gives them several more good years to go. No dope on that stuff, a ferrule only!