Red Seal Gasfitter — Class A Practice Exam

What type of pipe is most commonly used for underground natural gas systems?

1. Polyethylene (PE) pipe

2. Steel pipe

3. Copper pipe

4. PVC pipe

The correct answer is: Polyethylene (PE) pipe

Polyethylene (PE) pipe is the most commonly used material for underground natural gas systems due to its excellent properties, including resistance to corrosion, low weight, flexibility, and the ability to handle the pressures typically found in gas applications. The material is non-reactive, which means it will not corrode over time when buried, making it a durable choice for underground installations. PE pipe is also resistant to damage from soil movements or shifting, which can be important in areas prone to geological activity. Its installation process is relatively straightforward, often allowing for trenchless techniques that minimize disruption to surface activities and the environment. In contrast, while steel pipe can be used for natural gas applications and offers high strength, it is more susceptible to corrosion unless properly coated and maintained. Copper, while effective for certain gas applications, is generally not used for underground installations due to its higher cost and potential for theft. PVC pipe is not suitable for gas applications as it cannot withstand the necessary pressure and is not designed for handling flammable gases, making it inappropriate for this particular use.