Do brass female compression couplings always have a 'G' thread (BSP Parallel thread)

[Biilee]

Hi, do brass female straight compression couplings always have a 'G' thread (BSPP thread / BSP Parallel thread)?

I ask this because it's likely that I will have to replace a failed water hammer arrestor on the cold feed pipe that leads into my combi boiler and the replacement arrestor that I have in mind to use has a male 'G' thread (rather than a male 'R' thread / BSPT thread / BSP Tapered thread). I understand that the female brass straight compression coupling that the arrestor will have to fit into will therefore need to have a 'G' thread too (and not an 'R' thread).

So, it is safe for me to assume that the brass female compression coupling will be a 'G' thread or could it just as likely be an 'R' thread?

Many thanks if you can advise.

 

[stevetheplumber]

Re: Do brass female compression couplings always have a 'G' thread (BSP Parallel thre

lots of tape or a 1/2 flat washer in the fwemale

 

[Ray Stafford]

Re: Do brass female compression couplings always have a 'G' thread (BSP Parallel thre

No, you can't make that assumption. MOST (but not all) 15mm compression fittings have a 1/2" BSP thread, but some use other thread standards. Kuterlite for example use a much finer thread. As a rule of thumb, the more recent the design/product, the more likely it is to be 1/2 BSP.

 

[Biilee]

Re: Do brass female compression couplings always have a 'G' thread (BSP Parallel thre

Thanks for your reply, Ray.

So - just to clarify - most of these couplings are G thread (BSPP) rather than R thread (BSPT)?

 

[buckley plumb]

Re: Do brass female compression couplings always have a 'G' thread (BSP Parallel thre

same issue on hobs why don't hob manufacturers make them with a compression fitting most cylinder fittings are now

 

[Biilee]

Re: Do brass female compression couplings always have a 'G' thread (BSP Parallel thre

I think what I'll do - to save time and too much messing about - is buy two arrestors, i.e. the G thread one (that I would prefer to use as it looks to be of superior quality and is allegedly likely to perform better because of its more 'squared off' shape) and an R thread one to use instead - should the compression coupling turn out to be R thread. (Thank God for returns policies!)

 

[Plumbstar Tom]

Re: Do brass female compression couplings always have a 'G' thread (BSP Parallel thre

my money is on the G thread

 

[Biilee]

Re: Do brass female compression couplings always have a 'G' thread (BSP Parallel thre

Thanks, Tom - I hope you're right

 

[lame plumber]

Re: Do brass female compression couplings always have a 'G' thread (BSP Parallel thre

who invented alphabet threads, bsf etc is all I know about

 

[Biilee]

Re: Do brass female compression couplings always have a 'G' thread (BSP Parallel thre

An update: As thought, the coupling in question turned out to be a G thread (BSPP) rather than R thread (BSPT) so the G thread water hammer arrestor fitted okay.

I used PTFE tape but the joint leaked, so I tried gas PTFE tape instead and that worked with one and half winds of the tape. However, I believe I must have over tightened the arrestor into the coupling as it's leaking at the far end of the coupling now (whereas it wasn't before)...perhaps because the olive has failed. So I am going to try and replace the olive or the olive plus a new coupling to see if that works to cure the leak.

(Any tips re doing this will be gratefully received.)

 

[Biilee]

Re: Do brass female compression couplings always have a 'G' thread (BSP Parallel thre

A further update: I took the coupling off and discovered that the olive was pretty much immoveable, although the jointing compound that had been used was still moist/pliable on the outside of the olive...

So I did a surf on the Internet and found a very helpful YouTube video which suggested ways of dealing with leaking compression couplings, stuck olives etc., and from that decided to opt for putting a few wraps of PTFE tape either side and around/over the olive. This seemed to be the easiest and quickest possible solution (especially as the plumber advised that in all his years of being a plumber this method had never failed to stop such leaks for him...and I didn't fancy trying to hacksaw the olive off the pipe)...And, it has certainly done the trick for me (so far anyway, fingers crossed!).

Just thought I'd mention this in case any plumbing novices like me are faced with the same problem. (I would post a link to the Youtube video mentioned, but I'm not sure whether forum rules permit; however, for anyone wanting to see it, I hope it is okay for me to say go to YouTube and type in 'FIX LEAKING COMPRESSION PIPE FITTING - Plumbing Tips' and it should then come up at the top of the search list.)

Thank you to all who replied to this thread giving their advice