Hello--

I'm trying to install a new faucet. The water supply line on my OLD faucet is labeled 1/2" FIP Soft Cone x. 1/2" FIP Soft Cone. It plugs in to a T-type adapter that is connected to the valve (the dishwasher is also connected to the T).

The new faucet comes with its own water supply line, which I believe is a 3/8". I need to connect this water supply line to the T-adapter on the valve, and my clue is that what was once attached to it was labeled 1/2" x 1/2" as I wrote above.

So, I bought an adapter labeled 1/2" Female Comp. to 3/8" Male Comp. It seemed like it should work. And, the 3/8" end screws onto the water supply line attached to my new faucet just fine. But, the other end is JUST A TINY BIT too small to fit onto the T-adapter on the valve. We're talking fractions of an inch, such that I suspect it's not just a matter of getting the wrong size.

Did I miss some significance to the "Comp." vs. "FIP" thing, or is it possible that I am trying to attach my new faucet's water supply line to some kind of non-standard-sized connection? Or are there many different sizes that are close to 1/2" but not quite 1/2" (I didn't see any at the hardware store), and I just got the wrong size adapter?

Any help or insight on this would be appreciated. I have never done anything with any sort of plumbing before.