Steel pipe size identification

[jaydebruyne]

i need to cap this pipe under the floor, will need to remove the elbow and fit a cap. Not sure what size the pipe is. 1/2 inch??

 

[ShaunCorbs]

looks 1/2 should measure 3/4 od

3/4 should measure 1" od

 

[jaydebruyne]

looks 1/2 should measure 3/4 od

3/4 should measure 1" od

Looks more like 1/2 outer diameter???

 

[ShaunCorbs]

could be 3/8

 

[Scott_D]

Take a selection of caps and plugs
Might be easier to wind out the brass bit

 

[chris watkins]

normally 3/8" to gas fires.
Take the valve out if at all possible.
Test before starting.

 

[chris 8019]

i use steel pipe for non plumbing uses (industrial decor) that looks like 3/8 if you can take a photo against a rule i check against the sizes i have in stock looks too small for half inch not trying to sell just give advise ive got all sizes of black pressure pipe in my workshop so will be able to give a definite answer

 

[Last Plumber]

It does look like 3/8" to me but it is always difficult to tell off a photo.
Normally the O.D. of steel measure roughly the next size up to what it is. There and thereabouts. Or if you look at a fitting on the steel it may say the size on one side.