I just bought some blue Plastic water pipe '' T '' pieces .

 

I looked at the marking on those '' T '' pieces and it showed the size as being 1'' X  1'' . 

 

But when I measured the actual '' T '' pieces internal diameter , it measured 1 - 1/4 inches .

 

How can the actual markings show 1'' X 1 '' and the internal measurement actually be 1 - 1/4 inches .

 

What am I missing .????

 

The 1" is the nominal pipe size (NPS), effectively measured half way through the wall thickness of the pipe that goes in the fitting (it isn't quite that simple as various wall thicknesses are available with the same outside diameter and NPS).

 

Fear not 1" pipe will fit just fine.

 

If you actually want a hole about 1" across get 3/4" fittings.

You must take into consideration the wall thickness of the pipe which will be inserted into those tees

1/8" wall x 1/8" wall equals 1" ID

Most Tee and couplers are Female

Altho they do make street style ones where one branch is male

What you are measuring is the od of the pipe that goes inside that “ T “ , what is the id of the pipe ?

 

As Crossy said above, there are different wall thicknesses but the pipe that goes inside that “ T “ will have an id of 1” more or less.

As I understand it, the nominal size of pipe is based on the ID. As the OD must remain constant, the ID shrinks with wall thickness. 

 

The nominal size of tubing is generally based on the OD, but as with pipe, the OD is constant. 

 

 

Has a great table of PVC pipe sizes.

Easy as said. Pipe is sized by internal diameter and tube is sized by external diameter.

11 hours ago, VocalNeal said:

Easy as said. Pipe is sized by internal diameter and tube is sized by external diameter.

555 You are in Thailand and some parts are quoted in Imperial and others in metric. Fun, isn't it.

^ Quoted in inches but manufactured in mm. For DIY plastic by the pipe and fittings in the same shop?

What are you missing? For a T-piece 1" you are missing 3 pipes, each 1".