Roger Mills wrote:

On 10/01/2017 20:23, Roger Hayter wrote:
I have a Myson fan assisted radiator with 3/4" female brass connections
to the heat exchanger. Would it be better to use 3/4" taper fittings
with PTFE or Loctite stuff or 3/4" parallel ones with a fibre washer?
The taper ones make better sense to me, but is there any risk of
splitting the connections if they are as cheap and nasty as most things
are these days?



(By the way, I am seeing 19mm brass threads in the catalogues now - are
they some evil EU standard instead of BSP?)


What makes you think they are 3/4" BSP? If they measure around 20mm,
chances are that they are 1/2" BSP.

[With BSP the size relates to the nominal bore of an iron pipe with a
thread on the outside - so if the bore is 1/2", the thread is bigger
than that, and is actually a bit more than 3/4"]

See https://en.wikipedia.org/wiki/British_Standard_Pipe and scroll down
to the size table.

The fact that they are considerably bigger than 1/2" BSP (combined with
the rarity of 5/8" BSP) and that the fitting instructions for the
equipment state that they are 3/4" BSP combine to convince me. To the
extent I haven't bothered to measure them! The way the thing is packed
(and I have to send it back as it is broken) make it somewhat difficult
to measure anyway.
--

Roger Hayter