Question: [![enter image description here](https://i.stack.imgur.com/1gO9Z.jpg)](https://i.stack.imgur.com/1gO9Z.jpg)

Hi there, 

This is some piping to my Saxon hot water system. Just above where the white/green corrosion is is where the leak is.

My question is, can I use plumbers tape on the outside of this to seal the leak? 

I do not want to pull it apart as I don't know what I am doing. I am basically after a quick fix and thought plumbers tape (teflon tape) would suffice. If not are there any other options? (other than the obvious in getting a plumber out (again!).

Answer: 
Your other option is to ditch compression fittings and **learn how to sweat** (solder) copper pipe. Or if you do have a plumber come out, have them replace every accessible compression fitting with sweat fittings that will never leak ever again.

Compression fittings are prone to leakage, even when they aren't eating away your pipes with galvanic action, as you can see they are, with the black patina on that old stub.

I'm pretty sure **Stack Exchange can help you** with every aspect of learning how to solder, and if you're willing to do the work, the cost of the tools and materials will probably be less than a service call, and then you'd have the tools and the talent for work in the future. Having one easy elbow to sweat is a great place to start.

If you know anyone who knows how to sweat pipe, they should be able to show you how, *and* you'd be done, in under an hour: for the cost of a torch, solder, flux, fittings, a piece of sandpaper and a six pack of beer.
The fitting must be disassembled, cleaned and then apply teflon pipe dope to the threads and tighten snug. Once snug turn 3/4 turn and stop. Over tightening compression fittings will damage the collar under the nut and the pipe. If this does not work the pipe and collar may be damaged and need to be replaced.