I'm trying to plumb up an old cast iron radiator. I've got 2 new 1
1/2" threaded inserts which screw into the body of the rad. Into these
go the valves.

I've used PTFE tape on the threads but don't seem to be getting a
sealed joint on one end. Is there a technique for this? Alternatively
there's a cement called plumber's mait, which I think might be the
sealant originally used on cast iron rads.

Is this any good?

On 28 Mar, 19:32, andyv wrote:
I'm trying to plumb up an old cast iron radiator. I've got 2 new 1
1/2" threaded inserts which screw into the body of the rad. Into these
go the valves.

I've used PTFE tape on the threads but don't seem to be getting a
sealed joint on one end. Is there a technique for this? Alternatively
there's a cement called plumber's mait, which I think might be the
sealant originally used on cast iron rads.

Is this any good?

No

Try getting hold of some hemp fibre and a small pot of BOSS White or
Hawk White. Wrap the hemp fibre into the thread and rub on some of the
white. Screw into the rad until tight. If any moisture weeps by the
join it soaks into the hemp which swells and forms a seal. Traditional
ways are often the best when threaded joints leak. Just don't get
white onto immersion heater threads as you will have no end of
problems in removing the heater when it fails!

"andyv" wrote in message
...
I'm trying to plumb up an old cast iron radiator. I've got 2 new 1
1/2" threaded inserts which screw into the body of the rad. Into these
go the valves.

I've used PTFE tape on the threads but don't seem to be getting a
sealed joint on one end. Is there a technique for this? Alternatively
there's a cement called plumber's mait, which I think might be the
sealant originally used on cast iron rads.

Is this any good?

Loctite 55 PTFE string.

http://www.screwfix.com/prods/42142/...-Seal-Cord-50m

You will never use another product again.

Loctite 55 PTFE string.

http://www.screwfix.com/prods/42142/...ccessories/Loc...

You will never use another product again.

Seconded.

I've used it for an immersion heater to cylinder, and a very damaged
3/4" thread - both perfect seals first time.

andyv wrote:
I'm trying to plumb up an old cast iron radiator. I've got 2 new 1
1/2" threaded inserts which screw into the body of the rad. Into these
go the valves.

I've used PTFE tape on the threads but don't seem to be getting a
sealed joint on one end. Is there a technique for this? Alternatively
there's a cement called plumber's mait, which I think might be the
sealant originally used on cast iron rads.

You do need a lot of PTFE tape. 8 - 10 turns sometimes. Plumbers Mait is
wonderful stuff for cistern/pan joints, waste pipes etc.


--
Dave - The Medway Handyman
www.medwayhandyman.co.uk

In an earlier contribution to this discussion, andyv
wrote:
I'm trying to plumb up an old cast iron radiator. I've got 2 new 1
1/2" threaded inserts which screw into the body of the rad. Into these
go the valves.

I've used PTFE tape on the threads but don't seem to be getting a
sealed joint on one end. Is there a technique for this? Alternatively
there's a cement called plumber's mait, which I think might be the
sealant originally used on cast iron rads.

Is this any good?

I assume that the leak is on the 1 1/2" thread where the reducer screws
into the rad? This is most likely due to the threads in the rad being
grotty - probably with hardened residues of old Boss White, which are
tearing the PTFE tape.

You really need to clean up the treads with a 1 1/2"BSP tap. If you don't
have one (I'd be surprised if you *did*!), you can make an acceptable
substitute using an old male fitting and cutting some slots at right angles
to the threads with a Dremel or equivalent.

Failing that, you could use gas-grade PTFE tape which is a lot tougher than
the normal stuff. Or you could even resort to Boss White and hemp - which is
probably what was used on the radiator in it's former life.
--
Cheers,
Roger
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Please reply to Newsgroup. Whilst email address is valid, it is seldom
checked.

On 28 Mar, 20:53, "Vortex5"
wrote:

Loctite 55 PTFE string.

http://www.screwfix.com/prods/42142/...ccessories/Loc...

You will never use another product again.

What's the difference between this and ordinary PTFE tape that has
been twizzled (technical term!) into a thread?

Cheers.

What's the difference between this and ordinary PTFE tape that has
been twizzled (technical term!) into a thread?

It's white synthetic fibre, not ptfe - I think. It's more like an
ultra-heavy-duty dental floss (more like the thickness of lacing cord
if you're familiar with that), with what feels like a waxy coating on
it. Let's call it dental floss for alligators.

I suspect because it's manufactured to be a cord, it has a reduced
tendency to chew up when being used on a rather rough or damaged
thread, and withstands quite a bit heavier mechanical loads. It's
certainly not a cord you can stretch or break between your fingers,
the box has a little dental-floss style cutter on it.

However the *practical* difference is that a damaged thread that I had
unsuccessfully tried to seal several times with tape (eventually going
as thick as I could - still without eliminating a very slight weep) -
sealed first time with this stuff.

And that or similar seems to be a common experience.

Considering the hassle of re-pressuring and still finding a slight
weep (which maybe you can cure, maybe you can't), I suspect many
people will spend a little more if they're likely to get a first time
perfect seal.

On 29 Mar, 13:50, " wrote:

...Let's call it dental floss for alligators.

Ahh! Thank you very much. I shall have to invest in some of this
wonder material!

Cheers.

On 29/03/2010 13:05, David Paste wrote:
On 28 Mar, 20:53,
wrote:

Loctite 55 PTFE string.

http://www.screwfix.com/prods/42142/...ccessories/Loc...

You will never use another product again.

What's the difference between this and ordinary PTFE tape that has
been twizzled (technical term!) into a thread?

Cheers.


Everything you ever wanted to know is he

http://www.loctite55.co.uk/

and he

http://www.loctite55.co.uk/oem/55/_gfx/55_EN.pdf

Everything you ever wanted to know is he

http://www.loctite55.co.uk/

Lol at "portable water" for "potable water".

On Mar 29, 2:47*pm, " wrote:
Everything you ever wanted to know is he

http://www.loctite55.co.uk/

Lol at "portable water" for "potable water".

and "telfon"

Many thanks. Looks like Loctite 55 is the one for me.