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: 
No. "Teflon tape" is used on the threads of joints, not to seal leaks outside of joints. It's not adhesive like tape, so it wouldn't stick to the outside of the pipe at all.

If you don't know what you're doing, I'd bring in someone who does. Based on the amount of corrosion, it looks like it's been leaking for some time. It could be as simple as tightening the nut, or it might require disassembly and reassembly (possibly with new parts).
Wrapping externally with teflon tape wouldn't help. Teflon™ doesn't stick to **anything**; the only reason it works when used properly (wrapped on threads before assembly) is that it's squeezed tightly between the external and internal threads (using Teflon reduces friction so the joint can still be fully tightened).

The leak is at a [compression fitting](http://www.naturalhandyman.com/iip/infplumb/infcomp.html). The real way to fix this would be to disassemble, clean the nut and seat, trim the last 1" from the end of the copper pipe, install a new ring, and then reassemble the joint. If you can't disassemble it, then you might get away with cleaning off the corrosion with a wire brush and applying some sort of caulk or glue (perhaps an epoxy), but especially as the joint is hot it will be tough to find something that will last.