wHY DID THE PTFE TAPE wind off the thread Plumber?...was it because he didnt wind the tape on tightly when dressing the fitting or some other reason(i would love to know why? please?)...i only use hemp because it is bullet proof...but on the odd ocassion i use ptfe for example a female trap connector on to a basket waste/or a 8mm plastic water filter connection but have never been taught on the correct use of ptfe i just found myself that if you wind it/stretch it on tightly to the thread so it gets pulled into the fitting it will work but any movment could result in leakage...and behind the wall fittings where you have no means of testing you need to use a method (like hemp) where you know it will swell to ensure a watertight fitting.....I have got my boss into the habbit of putting our 80mm vanity nipples in with a brass cap on them before pre line inspection to ensure no leakage is happening...it also makes fit off a hell of a lot easier as vanitys can be a prick to work in esp wall mounted ones.

I agree with you thunderhead. I think every apprentice needs to know how to hemp properly before they touch PTFE or learn to use a screwdriver before they start using the cordless drill LOL. 

The problem with our NZ threads is that they are not tapered (unless your using galv) so the PTFE needs to be applied in a tapered form, start thin then thicken up as you work back (cone shape). On this specific job the plumber (well spotted Robbo!) simply didn't roughen up the thread, as he was winding in the thread the PTFE was winding out.

Some guys are aware of the fact that you need to buy brass fittings that are tapered (usually gas) but in most cases these fittings don't have the DR stamp on them (dezincification resistant) this simply means you cant bury them. so need to be careful. 

cheers for the info guys...i wasnt sure if you had to roughen up the threads like hemp but know i know and work the ptfe tape into a cone shape when using cheers peoples for that info...but i am and will always be a lover of hemp lol

hope your not like this with your coustomers plumber 

>> How much PTFE (thread tape) do I put on a thread?

Hi Guys, I thought I would update this thread because I have been asked this question last week. Any alternative answers are welcome.

I have been taught to apply the following formula [Diameter of thread x 2 / 10= total rounds (full 360 degrees)]

So if you have a 15mm thread its 15x2=30/10 = 3 times or if you have a 80mm pipe then its 80x10=160/10 = 16 times. Hope this helps.

By the way I always add just one more to the result