Why is it called 1/2 inch ?

[Ibrahim Kalay]

Hello,

Could someone please tell me why is it called 1/2 inch - 15mm standard blanking plug / bleeding valve?
Where ever I have measured I cant get 1/2 inch.

 

[ManchesterGas]

1/2 inch was the internal diameter of the pipe that was used with that size thread fittings

 

[SimonJohns]

It's 1/2" bsp thread

 

[ManchesterGas]

British Standard Pipe.

 

[chris watkins]

Should be BSPT really, which as you have all said stands for British Standard Pipe Thread, sized are 1/2", 3/4,1,1.1/4,1.1/2, 2" etc.
The metric equivalents are now being used 15,20,25,32,40,50mm a bit more.

 

[jtsplumbing]

It's a good old British measurement been used for years, not your foreign rubbish measurement's

 

[rpm]

Thought the T denounced a tapered thread, now where is the old Zeus book when you need it.

 

[tamz]

Anything with threads is in imperial sizes eg 1/4, 3/8, 1/2, 3/4 and so on and comes from, as Manchester gas said, the internal diameter of the relevant pipe.
In the UK we know them as BSP threads. British Standard Pipe. This thread comes in 2 types. BSPP (parallel) and BSPT (tapered).
This thread sizing also applies to European ISO standards where BSPP is known as G eg. G 3/4 and BSPT is R eg. R 3/4.

The thread on the plug and airvent are 1/2" BSPP or G 1/2

 

[rpm]

From what I can see there are 4 different BSP threads, one is parallel two are tapered with either a 55 or 60 degree taper but then there is another called BSPF which I think might be gas related.

 

[rpm]

tamz beat me to it.