The formal name for the orange plastic natural gas piping is Polyethylene (PE) Gas Pipe, specifically High-Density Polyethylene (HDPE). It is also commonly referred to as Orange Pipe.

Here's why it's called that:

* Polyethylene (PE): The material the pipe is made of, a type of plastic.

* High-Density Polyethylene (HDPE): A specific type of polyethylene with a high density, making it strong and durable.

* Orange: The distinctive color used to identify natural gas piping.

However, it's important to note that the color orange is a common identification for natural gas piping, but not a guarantee. Always check the markings on the pipe itself to confirm its intended use.