If connections between steel pipe and copper pipe are needed, which fitting is appropriate?

The appropriate fitting for connecting steel pipe to copper pipe is an adapter. This is because an adapter is specifically designed to connect two different types of materials or pipe fabrics, allowing for compatibility in size and type. For example, the differing thermal expansion and physical characteristics of steel and copper can create challenges in direct connections, which an adapter is built to handle effectively.

Using an adapter facilitates a secure and reliable junction between the two materials, ensuring that issues like leaks or disconnections are mitigated. Unlike couplings, which are used to connect two pipes of the same type or material, or elbow and union fittings that serve more specific purposes (turning the direction of flow or allowing for easy disconnections, respectively), an adapter is the dedicated solution for mixed material connections such as steel to copper.