What is the Difference Between Sanitary Tubing and Pipe?

November 13, 2013
Sanitary Tubing is Always Measured as Tube OD

Sanitary Tubing is Always Measured as Tube OD

We are asked this question a lot.  In everyday conversations, the words tube and pipe are often used interchangeably and understandably so.  But in the world of process piping they are quite different. In this post we are going to attempt to give the reader a simple, cogent definition of both and show how they are different.  To be sure, they are different.  If you have ever tried to mate a piece of 2” pipe to a piece of 2” tubing you know.

Pipe is measure in Nominal Pipe Size (NPS).  This is a standard set up in the mid 1900’s based upon different “schedules”.  The term schedule refers to the wall thickness of the pipe, the higher the schedule number the thicker the wall of the pipe.  All pipe schedules of a given size have the same OD dimension.  As the schedule number rises the ID of the pipe gets smaller, yielding a thicker wall.  What is interesting about pipe measurements is that no dimension of any schedule measures the stated pipe size.  If you take a 1” piece of pipe of any schedule, you cannot find any dimension measuring 1”.  Who knew?
The table below shows the dimensions of common pipe sizes in different schedules.

Size OD Inches

ID Inches

SCH 5 SCH 10 SCH 40 SCH 80 SCH 160
1/2″ .84″ 0.71″ .92″ .622″ .546″ 0.464″
3/4″ 1.05″ .920″ .884″ .828″ .742″ 0.612″
1″ 1.315″ 1.185″ 1.097″ 1.049″ .957″ .815″
1 1/2″ 1.9″ 1.77″ 1.682″ 1.610″ 1.50″ 1.338″
2″ 2.375″ 2.245″ 2.157″ 2.067″ 1.939″ 1.687″
3″ 3.5″ 3.334″ 3.760″ 3.068″ 2.901″ 2.624″
4″ 4.5″ 4.334″ 4.26″ 4.026″ 3.726″ 3.438″

Pipe is commercially available in a variety of materials from cast iron to stainless steel to PVC.

Tubing makes more sense.  Almost all domestic sanitary tubing and fittings are measured in tube size.  How do you measure tube size?  Simple, measure the outside diameter of the tube and you have the size.  One inch tubing measures one inch on the outside diameter, two inch measures two inch, etc.  Simple isn’t it?  Well not that simple.  As with most things in life, there are more nuances to deal with, namely wall thicknesses.  Tubing is offered in a variety of wall thickness.  These are normally called out as the actual thickness of the wall or in gauges.  The gauge number is a derived number that represents the various wall thickness available in tubing.  The higher the gauge number the thinner the wall.

Size OD Inches

ID Inches

18 16 14 12 10
1/2″ 1/2″ .402″ .37″
3/4″ 3/4″ .652″ .62″ .584″ 0.532″
1″ 1″ .902″ 0.87″ .834″ .782″ .732″
1 1/2″ 1 1/2″ 1.37″ 1.334″ 1.282″ 1.232″
2″ 2″ 1.935″ 1.834″ 1.782″ 1.732″
3″ 3″ 2.87″ 2.834″ 2.782″ 2.732″
4″ 4″ 3.834 3.782″ 3.732″

So there is a brief explanation of the differences between tubing and pipe.  So where do sanitary fittings and tubing fall within this matrix?  Here is where things get a little simpler. The world of sanitary tubing and fittings has standardized on specific gauges (wall thickness) per size.

1/2″ through 3”  16 Gauge             0.065” Wall

4”                            14 Gauge             0.083” Wall

6” and 8”              12 Gauge             0.109” Wall

10” and 12”         10 Gauge             0.134” Wall

 So what do you do when you need to match a piece of 2” pipe to 2” sanitary tubing?  You use an adapter.  Fortunately there are a wide variety of stainless steel adapters that will get you from the pipe world to the sanitary world.  There are male and female NPT X Tri-Clamp adapters, NPT X sanitary buttweld adapter and many more.

Hopefully this information brings a little clarity to the differences between stainless steel pipe and sanitary stainless steel fittings and tubing. Things get much easier when everyone is speaking the same language and you are confident in what you are saying, it takes a lot of the guess work out of ordering adapters.  We work in the world of sanitary process equipment every day.  So if you still have questions on this subject, contact us, and we will try to help.