Will this seal?

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Nigel R

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Morning. I have this connection to make, between 35mm copper pipe and a big Grundfos pump. The official Grundfos connector is this iron 1/14 bsp female. The brass adapter I've got screws in, too tight to do by hand but smoothly with a spanner. There's no mating face though, and it's a parallel thread. Will it seal, do you think, in a heating system, and if so what sealant would you use? Any advice gratefully received!
[GALLERY=media, 106957]20210824_093910 by Nigel R posted 24 Aug 2021 at 9:51 AM[/GALLERY]
 
Wrap a few layers of PTFE tape around the brass thread, before assembling, wind the tape on, evenly and in the same direction as you will be screwing the fitting on. It should need spanners to assemble, but not be too tight with the PTFE in place.
 
Parallel threads are not designed to seal via the thread, but by the face of the male part compressing on a seal at the base on the female part. You might be able to make them seal by using compound but it's a botch.

A tapered male fitted into a parallel socket or a parallel male fitted into a tapered socket is also a botch.
 
Jackrae said:
Parallel threads are not designed to seal via the thread, but by the face of the male part compressing on a seal at the base on the female part.
Click to expand...
Exactly! But this is the Grundfos part and it's the same on their website. There is a perfect mating face on the other end, but not this one. I have an enquiry in with them, I'm expecting them now to confirm that modern sealants do seal it.
 
Grundfos did reply, and indeed they said it seals in the threads with a sealant or ptfe.
 
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