How much PTFE is needed

[garrymum]

I am going to drain the central heating and fit TRV's to a few rads. How much PTFE tape do I need to wrap around the threads? Have got a new tail with the TRV so need to wrap PTFE around the tail which replaces the existing rad tail, then the 2 threads of the trv valve itself.

How many layers of PTFE is usually required?

Thanks

 

[Dick n Dom]

Garrymum...On the T.R.V tail i normally wrap it around 6-7 times and then run my finger nail around the thread afterwards,This will stop the tape slipping when you tighten it up...regarding the compression joints on the valve just use pipe jointing compound smeared over the olive before you join it up.

 

[Careful_Bodger]

Being a DIYer I perhaps do this incorrectly, but I use slightly fewer turns than D&D - maybe 4-ish. I find a pull on the final turn beds in the tape. I also put 2 turns around the olive or any other mating faces (I am thinking of the 'bullet' type ends to some tails). I have not had a leak yet

Another thing I have noted - and you might like to check this - is that the new tails I used were longer than the old. These particular ones have an external square nut, rather than an internal hex thingy, which makes them longer. I was lucky in that there was enough play in the feed and return pipes, and the rad's position on the brackets, to allow for the extra width required.

HTH

 

[chrishutt]

Just to stress something mentioned by D&D, many DIYers put PTFE tape around the threads of compression fittings (as you proposed to do). This is utterly pointless since the threads do not provide the seal. The threads are there to allow compression to be applied to actual mating surfaces (namely olive and recess in end of threads.

 

[Paul Barker]

I use plenty of turns of ptfe, anyone who works for me that gets a leak on a rad tail it's always because they don 't put enough ptfe on. I don't get leaks from rad tails. Put plenty on and then double it.

 

[Careful_Bodger]

Not sure I agree with

utterly pointless

since being PTFE the coefficient of friction is very low and allows better tightening of the joint.

Or have I missed something

 

[brumylad]

I never use ptfe tape on NEW compression fittings. As has been said, the friction is lost and personally can't tell when the olive starts to bite on the pipe. As a result I have overtightened joints in the past, deforming the olive or even cracking the nut.

I always use three or four turns of PTFE tape when remaking compression joints, but always applied to the olive, never the threads, this in my opinion looks unsightly and I agree is pointless.

 

[htgeng]

I always use three or four turns of PTFE tape when remaking compression joints, but always applied to the olive, never the threads, this in my opinion looks unsightly and I agree is pointless.

I've never used ptfe on olives. I would always renew olives if they look mishapen.

 

[ChrisR]

SOmetimes an olive will leak, then a bit of tape is ok, but no point usually. Chrome cheapo fittings like iso valves seem to be about the worst!
I agree with the above comments - more turns than you think should be plenty, and run your thumbnail round. If you have trouble withthe tape coming off, roughen the threads. I use the metal-saw on a Swiss penknife dragged across the threads. You will remember seeing some made that way.
Or bin the tape, and use Locktite 55. It's like dental floss but thicker. They say don't fill each thread but doing it that way seems to work best.

 

[Paul Barker]

I use Jet Blue on Olives if I have it to hand, or nothing. Always worth stocking up on Copper Olives.

 

[silverback]

Locktite 55 best invention ever

 

[ChrisR]

How do you use it? I find if you do it the way they say, sort of randomly, you get really tight spots. ?

 

[Dick n Dom]

On the subject of olives..Why do we have brass and copper olives is there a reason when a certain type should be used.

 

[JPC]

i put 12-15 wraps on a rad tail. very seldom have i had to unwrap it cos its too much.
jet blue on compression.
even old compression...new olive and jet blue...seems to work just fine.

ps...i laughed at a mate who bought an olive cutter.....nothing wrong with my hack saw, i said.
then one day i tried one whilst fittings trvs on old rads to the upstairs of the house. well brill....and paid for in one job alone due to time saved !