Why is solvent-cementing joints between different types of plastic not allowed?

Solvent-cementing joints between different types of plastic is not allowed primarily because they may not be reliable. Different types of plastics have varying chemical compositions and properties, which can affect their ability to bond effectively when solvent-cemented together. If the joint does not form a proper bond due to incompatibility, it can lead to leaks, failures, or even complete disconnection of the pipes under pressure or stress.

Reliable connections are crucial in plumbing systems to ensure safety and functionality. Therefore, regulations typically require that joints be made with compatible materials to maintain the integrity of the system and prevent potential hazards. This enforceable standard emphasizes the importance of adhering to specific guidelines when working with different types of materials in plumbing applications.