Why is it called 1/2 inch ?

[tamz]

BSPP is also known as BSPF (fitting). The threads are 55º. The same as Whitworth.

 

[Ibrahim Kalay]

Thanks for your replies.

I knew it was something to do with pipe rather than blanking plug / bleeding valve.

 

[chris watkins]

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

Thanks Tom, I stand corrected, you have also explained why T&P safety valves are denoted in sizes such as G 1/2 & G 3/4 etc.which I never new, still as they say, every day's a school day. :dunce2:

 

[Masood]

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.

Ever thought about writing a book, Tam? Or making YouTube videos about plumbing principles, history etc? You've a head full of information that most of us will never come across unless people like you pass it on...

 

[kendod]

old school plumbing lol