Understanding Pipe Classes and Pressure Ratings of Pipe

All pressure pipe is designed for handling and conveying fluids that are pumped at pressure. 

Each pressure pipe has a Class or Pressure Rating, which indicates the pressure at which the pipe can be expected to function in this capacity for sustained periods, this is often referred to as working pressure or operating pressure.

Imperial Pipe is referenced by Class, whereas Metric tends to be referenced by a PN number, which means "Pression Nominal". The designator 'PN' is followed by the rating that is measured in bars, so for example, PN16 pipe has a 16 bar rating.

The greater the pressure rating of a pipe usually tends to mean a thicker wall to handle the increased pressure, which means more product and an associated increase in the cost, but using the chart below you may keep the cost as low as possible without compromising the longevity of the pipe once installed.

One of the main points of this article is to draw attention to the relationship between the temperature of conveyed fluid and working pressure of the pipe, because as the temperature of a conveyed fluid increases it affects the pipe and the working pressure should decrease accordingly, this is known as de-rating. 

See the following charts as a guide to de-rating.

Both ABS pipe and UPVC pipe are available in the imperial system in Class C, Class D, Class E and Class T.

UPVC pipe is widely available in Metric with the following pressure ratings: PN10 & PN16

ABS metric: whilst available, it is comparatively expensive, as it is only produced by one manufacturer worldwide. Pipe Warehouse UK, therefore does not hold a general stock of metric ABS pipe or fittings, however, we could help facilitate you if your job demands Metric ABS.

You'll notice that Pipe Warehouse UK does not hold a general stock of Class D pipe, this is because there's generally very little price difference between Class D pipe and Class E pipe making the Class E pipe much more popular as it is capable of handling greater pressure.

Class T Pipe

Class T pipe (also referred to as Class 7) has the thickest wall diameter of all classes that we've discussed. Therefore you may think it has the greatest pressure rating; however, there is more to the story. Class T pipe is designed so that the pipe itself can be threaded to accept threaded fittings, this scores away at the wall thickness reducing the pressure handling capability. For this reason, the pipe is rated as 12.0 Bar, which is the same as Class D. When choosing and using Class T with a thread, use the Class D de-rating information.

This chart shows the recommended maximum working pressures of UPVC pipe based on the conveyance of water at different temperatures.  Different pipe materials have different material properties, so can handle different temperatures, this chart is specifically relating to UPVC. This chart does not apply when piping any fluid that is any more aggressive than water, the piped media can affect overall performance of the pipe; as always, we recommend speaking to us if you need more information in this regard.

This chart shows the recommended maximum working pressures of ABS pipe based on the conveyance of water at different temperatures.  Different pipe materials have different material properties, so can handle different temperatures, this chart is specifically relating to ABS. This chart does not apply when piping any fluid that is any more aggressive than water,the piped media can affect overall performance of the pipe; as always, we recommend speaking to us if you need more information in this regard.

Understanding Classes of Pipe & Pressure Ratings

We have prepared an informative video that explains pipe classes & pressure ratings further