View Full Version : compression nut leaking on cold water to sink

09-06-2005, 01:08 PM
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?

Dunbar Plumbing
09-07-2005, 03:29 PM
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.

Gary Slusser
09-08-2005, 04:37 PM
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.

Quality Water Associates

09-08-2005, 06:49 PM
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.

09-08-2005, 09:10 PM
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!