What thickness of polyethylene is commonly used to insulate buried heating pipes to limit heat loss?

• A. 4 mil
• B. 6 mil
• C. 10 mil
• D. 20 mil

Answer: (B)

The main idea here is that the polyethylene layer around buried pipes acts as a moisture and vapor barrier that helps cut heat loss. A moderate thickness is chosen because it provides enough protection against punctures and soil moisture without making wrapping awkward or costly. The thinnest option is prone to damage during burial, while the thicker options add cost and stiffness without giving much extra benefit for typical installations. So, the commonly used thickness sits in the middle, giving a practical balance of durability, effectiveness, and value.