Brand New Bathroom Sink Hardware - Still Leaking

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Apr 26, 2023
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I had a leak under my guest bathroom sink on the cold water side.

Bought brand new supply valves (1/4 turn) and new supply lines.

Installed and noticed that now both sides were leaking. Remembering that the supply line had compression fittings and maybe I shouldn't have placed any teflon tape there, I removed the supply lines, stripped the tape off the threads and re-applied.

Still leaking, even with the valves closed, but the leak appears to be coming from where the supply line attaches to the valve, which is super odd. That shouldn't happen, right?

Did I mess up the fittings, somehow? Should I -for some reason - not have purchased 1/4 turn valves?

I'm really not sure what I'm doing wrong, but I feel like maybe it's time to call in a professional.

Any thoughts before I do that?

My thanks, in advance,

Finger tight plus 2-3 turns on those flex lines is usually all it takes.
Yeah I remember when I first started doing my own plumbing that one of the mistakes I made was overtightening the supply lines. Those little black gaskets leak very easily if you overtighten them.

My general way of doing any plumbing is this and it has helped me immensely. I only tighten a little at a time and then wait a while and check for leaks and tighten a little a time until all the leaks stop. It takes me a little longer than a professional but this is the best way if it's your own place and you have the luxury of time. I also check again the next day to make sure I got it.

I seem to always have to make adjustments like that for P traps too. The pro's get it right in seconds the first time by experience. I think the rest of us have to tighten a little at a time but always start with a little too loose, never too tight.
Compression fittings work via the ring on the supply pipe. You *might* have to replace the rings get leaks sorted.

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