BSPT radiator tail

[Fredxx]

I would normally use thick PTFE tape, but I'm not happy with the feel.

I used 150-200mm of tape and I can keep turning the tail onto the
radiator and if anything gets looser as I keep turning. Yes I have
wrapped in the right direction!

Is there any advantage to using thin tape, or is there a preferred or
recommended sealant which hardens to form a seal. Where some modest
torque needs to be applied to remove the tail (in the unlikely event it
need to be removed).

[Roger Mills]

It needs to seal on the threads before bottoming out. Screw the tail in
without any tape and see how far it goes in. Then take it out and wrap
it with tape. It needs to go tight before it goes in as far as it does
without tape. I always use tape designed for use for gas pipes. It's
thicker and stronger than the standard stuff.
--
Cheers,
Roger

[Fredxx]

The tails don't bottom out, this is an example of the type I have:

https://www.stevensonplumbing.co.uk/images/source/Plumbing/Valves/rad_valve_tail_2.jpg

I'm sure they won't leak, but the tails don't feel as secure as I would
like them to be.

[John Rumm]

On 20/02/2021 19:28, Fredxx wrote:

> I would normally use thick PTFE tape, but I'm not happy with the feel.
>
> I used 150-200mm of tape and I can keep turning the tail onto the
> radiator and if anything gets looser as I keep turning. Yes I have
> wrapped in the right direction!

You need *lots* of tape on those. Also there is a trick to winding it so
that it get thicker as you move further up the thread. So you probably
want 10 at the start then more as you move up the thread. I normally
wind the tape "side on" for the last few turns so that it folds and
makes narrower double layers for the last bit.

> Is there any advantage to using thin tape, or is there a preferred or
> recommended sealant which hardens to form a seal. Where some modest
> torque needs to be applied to remove the tail (in the unlikely event it
> need to be removed).

There are liquid PTFE type products, and also Fernox LS-X which sets. So
people favour PTFE cord or string since you can build up thicker layers
more easily, and its easier to make a taper thread lock up.


--
Cheers,

John.

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[Fredxx]

On 21/02/2021 00:47, John Rumm wrote:
> On 20/02/2021 19:28, Fredxx wrote:
>> I would normally use thick PTFE tape, but I'm not happy with the feel.
>>
>> I used 150-200mm of tape and I can keep turning the tail onto the
>> radiator and if anything gets looser as I keep turning. Yes I have
>> wrapped in the right direction!
>
> You need *lots* of tape on those. Also there is a trick to winding it so
> that it get thicker as you move further up the thread. So you probably
> want 10 at the start then more as you move up the thread. I normally
> wind the tape "side on" for the last few turns so that it folds and
> makes narrower double layers for the last bit.

I actually tried that, but after a certain thickness it just stayed put
and didn't wind in with the fitting.

>> Is there any advantage to using thin tape, or is there a preferred or
>> recommended sealant which hardens to form a seal. Where some modest
>> torque needs to be applied to remove the tail (in the unlikely event
>> it need to be removed).
>
> There are liquid PTFE type products, and also Fernox LS-X which sets. So
> people favour PTFE cord or string since you can build up thicker layers
> more easily, and its easier to make a taper thread lock up.

After your suggestion I came up with:
https://www.youtube.com/watch?v=JC4fvZF-M-g

The Flomasta version claims to be Nylon and silicone thread sealant.
https://www.screwfix.com/p/flomasta-pipe-sealing-cord-80m/2272v

I hadn't come across roughening up the threads and perhaps can now see
why some BSP fittings come like this.


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