What is an allowable pipe material for use in an earth heat exchanger of a hydronic heating system

Galvanized iron is prone to corrosion over time, especially in the presence of moisture and various fluids typically encountered in hydronic systems. This vulnerability can lead to leaks and system failures, making it unsuitable for long-term use in earth heat exchangers.

While PVC is a lightweight and cost-effective material, it has limitations in temperature tolerance and can become brittle in extreme conditions. The thermal conductivity of PVC is also less favorable for heat exchange applications compared to other materials, restricting its effectiveness in hydronic heating systems.

Although 304 stainless steel offers excellent corrosion resistance and strength, it is often more expensive and heavier than alternatives like polyethylene. Additionally, its thermal properties may not be as efficient in transferring heat compared to other materials specifically designed for heat exchangers.