Plumbing thread - BSP or not BSP, that is the question

[Jonathan Webb]

Hello,
I'm fitting a new vented copper cylinder. The coil bosses seem to be 1"BSP & the couplers I bought for these seem to fit ok, but the feed and outlet aren't 3/4". These measure about 28.4mm across and I can't find any info on what this is as it's between BSP sizes (I would have thought enough to rule out mismeasurement)

Have looked online and cylinder manufacturers don't seem to go beyond "industry standard coil connections" ‍.

The nut on my 22mm Essex Flange also fits but that doesn't say either beyond "BSP threaded" but then it fits the "non-BSP" boss on my cylinder.

Anyone able to shed some light on what the thread is or fitting should be? Many thanks

 

[Agroshield]

The nut on my 22mm Essex Flange also fits...

Do you mean the hex nut from your flange or the compression nut?

If a 22mm compression nut fits, the thread is likely to be 22mm compression nut.

As you surmise, this is not BSP, nor have I seen it written down anywhere.

Someone must know it as 22mm olive pullers (which screw into a 22mm compression nut) are made.

See here (last post of the thread):

22mm fitting thread size ?

Hello. Could anyone please advise ? What is the thread size found on a standard 22mm compression fitting ? It seems to be 14tpi and is slightly larger than 3/4bsp. Thank you, Pete.

forum.buildhub.org.uk

I would quibble over the characterisation of it as UNS because UN threads have a 60 degree angle and BSP 55 degree. An automatic machine producing those fittings would be unlikely to use two different tools.

 

[Blobber]

Is it a used/second hand cylinder? if so that fitting needs to come out and be replaced, a lot of the compression fittings can have odd sized threads

 

[Agroshield]

...if so that fitting needs to come out and be replaced...

That is a bit drastic. I would be trying every brand and supplier of nut to try to find one that fits before attempting to remove the fitting.

 

[Blobber]

That is a bit drastic. I would be trying every brand and supplier of nut to try to find one that fits before attempting to remove the fitting.

Hardly drastic, be a nice BSP thread to take something like this

Made4Trade Compression Coupler Male

• The only compression fittings range manufactured in the UK• Create a mechanical heat free connection• WRAS Approved• Suitable for use on both gas and water• Suitable for Domestic and Commercial Heating and Plumbing Applications• 25 Year Warranty • Manufactured to EN1254

www.toolstation.com

 

[carbonarc]

The olive remover I have for 22 mm copper pipe fittings has a threaded spigot diameter of 28.4 mm. The screw pitch of the puller is 1.75 mm and thread angle is 60 degrees.

 

[gaz1]

most cylinder connections are these for the sides and the top connector

Made4Trade End Feed Straight Cylinder Union

End feed capillary fitting is part of the Made4trade range and manufactured to BS EN 1254-1. This fitting joints copper tube manufactured to BS EN 1057 using solder.It is suitable for above ground hot and cold domestic or potable water services, central heating systems, low-pressure steam...

www.toolstation.com

 

[hunter27]

Compression fittings often have their own threads for joining the 2 parts of the fitting together, Obviously the end thread for connecting to the plumbing is 1/2", 3/4" 1" BSP etc. It was annoying changing a 3 port valve in a cupboard with water dripping out and finding the threads were often finer than the valve you were replacing requiring replacing the old nuts and olives while trying to catch the water. More often than not 1/2" comp fittings also had a 1/2" BSP thread but I have never seen that on any larger fittings.
Most cylinders now come with the compression fittings moulded into the cylinder.

 

[Agroshield]

...thread angle is 60 degrees.

How are you measuring that thread angle? Or, more specifically, what are you using to measure the thread that can distinguish between a 60 degree and 55 degree thread angle?

Please also consider the relationship between 28.4mm and 1 1/8" and 1.75mm pitch and 14tpi pitch.

Given that 14tpi is used in both NPT and BSP fittings, and 1.75mm pitch is used almost nowhere apart from ISO M12, a balance of probabilities approach might point away from a metric thread.

 

[Memmeddu]

Might be NPT?

 

[Smallfry]

Might be NPT?

Yes. What I was thinking. Had to fit some plugs in a heat exchanger that I thought were 3/8 BSPT. They turned out to be NPTT. I could have forced them in but decided not to.

 

[nickk]

I find the same on some of my core drills,some are 5/8” some 22mm.

 

[Kayos]

If it's not BSP it will be a cylinder union

Clue is in the name

 

[Agroshield]

If it's not BSP it will be a cylinder union

Please could you find me a fitting called a cylinder union that does not have a BSP thread.

Every single cylinder union I find is described similarly: 22mm x 1" or 28mm x 1". In every case, the imperial number is the BSP thread size. There is nothing to be found that is not BSP and the very first post above clearly establishes that the thread is not BSP.

 

[S-Rail]

Looking at it , you just want 2 nuts and 2 olives from a 22mm compression fitting . Most new cylinders come with them , so you can just pipe up and go ….

As others say they won’t be BSP , but you shouldn’t need any special fittings to make it work . Just the nut and olives .. as most domestic pipe work will be 22mm pipe work unless specified differently .

On the heating coils you should just need some 22mm compression to 3/4 female irons . PTFE up the threads on the cylinder and fit .

 

[Kayos]

Please could you find me a fitting called a cylinder union that does not have a BSP thread.

Every single cylinder union I find is described similarly: 22mm x 1" or 28mm x 1". In every case, the imperial number is the BSP thread size. There is nothing to be found that is not BSP and the very first post above clearly establishes that the thread is not BSP.

Gaz's post has a link to the exact fitting, the 1" is BSP, sort of, but the shape of the fitting is what makes the seal

Otherwise it's normal bsp or compression

I've fitted hundreds over the years, cylinder unions are less common these days but still out there

 

[julianf]

As above, the copper will have a 1" bsp female thread in it that the brass fitting has screwed into.

The thread that you're measuring the OD for is just for the compression nut. There's only really a couple of types, a course modern one and a finer old one. There may be another coarse one, but if you have a few old 22mm fittings you should be able to find one to fit.


Removing the fitting from the tank could go fine or it could end in tears when the copper twists up and tears before the fitting comes loose. It's certainly way easier to just find a matching compression nut.

 

[waddycall]

Looks like it just needs a nut and olive. You can see the stop for the pipe inside the fitting. I’d be tempted to find a matching nut rather than take that fitting out if it’s been in a while. Who cares what thread it is if the nut goes on ok.

 

[Jonathan Webb]

Do you mean the hex nut from your flange or the compression nut?

If a 22mm compression nut fits, the thread is likely to be 22mm compression nut.

As you surmise, this is not BSP, nor have I seen it written down anywhere.

Someone must know it as 22mm olive pullers (which screw into a 22mm compression nut) are made.

See here (last post of the thread):

22mm fitting thread size ?

Hello. Could anyone please advise ? What is the thread size found on a standard 22mm compression fitting ? It seems to be 14tpi and is slightly larger than 3/4bsp. Thank you, Pete.

forum.buildhub.org.uk

I would quibble over the characterisation of it as UNS because UN threads have a 60 degree angle and BSP 55 degree. An automatic machine producing those fittings would be unlikely to use two different tools.

Thanks, yes the compression nut on the Essex flange. I hadn't considered a deformable fitting - had got focussed on these https://www.bes.co.uk/compression-straight-adaptor-22mm-x-1-17616/ I'd seen that post and although it contained a factual answer it wasn't much use as I need to know what fittings use that specific thread. There are responses here that point me in the right direction (I hope :-D )

 

[Jonathan Webb]

Looks like it just needs a nut and olive. You can see the stop for the pipe inside the fitting. I’d be tempted to find a matching nut rather than take that fitting out if it’s been in a while. Who cares what thread it is if the nut goes on ok.

Thanks. Removing the fitting is very low down on the list of things I want to do :-D