On 23/12/2020 20:26, charles wrote:
In article ,
newshound wrote:
On 23/12/2020 18:37, JohnP wrote:


Sealant on the treads is not the solution - the threads only provide a
clamping force. The olive forms the seal. Cleanliness is the most important
thing.

Agreed, absolutely. But occasionally you end up with one joint that
weeps and where it would be a PITA to replace because of all the other
stuff connected to it. And then those PTFE goos are very useful.

It is also one of the reasons I usually use PTFE tape on the threads of
new compression fitting builds, because it reduces the friction so that
you get a better clamping load with less torque.

People always tell you not to put the tape over the olive, and I don't.
Although actually if you compare the strength of PTFE with even fully
annealed copper, you will find that a thin layer of PTFE will completely
extrude away from the metal to metal interface. The same is true of the
"knife edge" that you get where brass olives dig into a copper pipe.
PTFE tape there is *not* going to prevent you from getting a seal.

But, in a bodge, it's always possible for tape to trap grit at the
sealing location and make things worse.

I was taught to put tape over the olive. It seesm to work - even 40 years
later.

I was taught it was something only done by amateurs. It's doesn't help
seal but may lubricate the threads.
https://en.wikipedia.org/wiki/Compression_fitting

If you are going to use lubricant on the threads Jet-Lube V-2 Plus is a
potable lubricant.