How any wraps on PTFE tape on a threaded drain off valve?

[Flookz]

Hello, I was wondering how many wraps of PTFE tape you need to use on a threaded drain off valve that is going to be fitted into a Telford horizontal stainless hot water cylinder. Thanks

 

[Scott_D]

Is it a new installation?
You need the G3 qualification to work on unvented cylinders

 

[Flookz]

Is it a new installation?
You need the G3 qualification to work on unvented cylinders

It is a new installation. The threaded drain off valve hasn’t been installed. I have the G3 qualification. But have only done the course recently and haven’t worked on my first cylinder yet. So I am just checking before I fit the drain off valve. I would normally use 3 to 4 wraps of PTFE tape. Thanks

 

[SimonG]

Just enough to seal and not too much to make it difficult.

It's a mystic art.

And dont forget the paste.

 

[Stigster]

I do 10-12 wraps and see if I can screw the fitting in by hand alone. If I can't I put the tools on it and do it all the way up. If I can do it up almost all the way by hand, I carefully unscrew it so as not to shred the tape up on the fitting and add another 5 or 6 wraps.

I used to always clean all the PTFE off and start from scratch, just adding more wraps of tape and give it another go if it didn't feel right or leaked. Then an old plumber told me to try what I describe above and I have had much more reliable joints ever since.

As Simon G says, it is a bit of a mystic art too and something you just get a feel for. Also plumbers like to disagree on the best way to do such things so anyone please feel free to disagree with my method! It works for me very reliably that's all I can say.

Now on to paste or no paste.......

 

[SimonG]

Depends on the quality of the materials as well. Some towel rails and radiators are complete tat and need more.

 

[Stigster]

Depends on the quality of the materials as well. Some towel rails and radiators are complete tat and need more.

I have had to use a 1/2" BSP tap to sort out the threads on some cheapo towel rails before. When the tappings are that bad it does become difficult to know how much tape will seal them. The again my method has worked fine on those ones too, especially after running the tap through them to clear the threads.

 

[quality]

A couple of dabs of 577 Sorted

 

[OffshoreGas]

A couple of dabs of 577 Sorted

Spot on, parallel threads aren't deigned to seal with PTFE tape.

 

[king of pipes]

Locktite 55 for me brass into stainless ptfe is risky 16 wraps is my choice for rad tails . Kop

 

[Stigster]

Spot on, parallel threads aren't deigned to seal with PTFE tape.

Some radiator tails are taper thread though. On the parallel ones, do you recommend using a string type sealer? I suppose good old hemp and paste would work on a parallel thread well too?

 

[OffshoreGas]

Some radiator tails are taper thread though. On the parallel ones, do you recommend using a string type sealer? I suppose good old hemp and paste would work on a parallel thread well too?

Everything I’ve seen in in UK domestic plumbing and heating has been BSP parallel, some of the wiser guys in here may know better. I guess you have more NPT stuff on the US?

You can often get away with PTFE because the pressure is low. Your generally recommended to use an anaerobic thread sealant like Loctite 577. You can get an activator to speed up the cure time.