Plumbing – How to change the final position of a threaded-in faucet

It may not be necessary to see all the threads "disappear" for the two ends to be fully engaged and tightened.

You could measure each end (male and female) to determine if they are substantially different to determine if the shorter of the two is fully engaged.

After you cover the male end threads with a couple winds of Teflon tape and thread them together very snug, (be careful not to over tighten) the important thing is that the connection does not leak. If you don't leak, you are all set, regardless if any threads on one side (feed line or faucet) are showing.

As the comments have pointed out, that is a compression fitting and not a threaded fitting. Removing it should be relatively easy. Loosen the nut by holding the valve with one wrench and turning the nut with another. Once it is loose enough, the valve should just pull off the pipe.

You will have to examine the exposed portion of pipe once you remove the valve to determine if you can re-use the pipe and valve as-is or if you need to cut it inside and install a new stub that you can then install a new valve on. I doubt you will be able to re-use it (its damaged already, hence the leak), so in all likelihood, you will have to replace it. If you do replace it, get a ball valve (1/4 turn) as they are more reliable and easier to operate.

Hopefuly you have an inside shutoff valve for this. If you don't, you will want to ensure you have everything you need before starting this project as the water to your house will be off. If you do have a shutoff then just close it and you can take as much time as you'd like.

Note that you should not use pipe tape or dope on compressing fittings.