Replace Ferrule Or Not, And Other Rookie Questions

I don't know if this is the equivalent to electrical outlets with the ground plug on the top or the bottom but I wanted to ask:

Should you always replace the ferrule when replacing a cut off valve?

I'm pretty sure that if it shows signs of wear or damage it should be replaced, but if it's in good shape, is it ok to reuse, would a good plumber reuse it?

This also might be the same type of question, I've read not to put anything on the threads of a compression valve, and some that say you should, thoughts?

Also, two more questions, what about teflon tape or equivalent on the two ends of the supply line, let's say on a toilet, yes or no?

Sorry about the rookie questions.

You Win! You are the one hundreth poster to ask this question ( and you will get about 40 replies also. Anyway, if the nut and ring are in good shape, and they fit the new valve go ahead and re-use them.

valve

Old valve OFF, new valve ON, period. No new ferrule unless the copper tube is damaged and has to be cut off, and no "compound" on the ferrule either.

3rd reply to the winner!

I would rather deal with 1000 ernest rookie questions that 1 from a know-it-all rookie.

To save time, perhaps there should be FAQ section for questions that get repeat business.

idea

Great idea, except it would be like a dictionary for words you don't know how to spell. No one would know where to find what they were looking for.

Best thing you could do is probably write up a generic answer to some of these FAQ's and save them on your PC for cutting and pasting. I've got a few that I usually go back and search for then cut and paste...

I'd probably be better off saving them on my own PC for reuse.
sometimes searching can be fun

Hey, I can speal just fine

How about a search that links to past post's?

There is a search function here and on other forums but I often find google to be more effective than the forum search engines...

Kinda like I know I wrote it where the hell is it!