Which of the following is a type of joint for high density polyethylene piping?

High-density polyethylene (HDPE) piping utilizes several types of joints, and thermal butt-fusion is one of the most common methods for joining HDPE pipes. This method involves heating the ends of two pieces of piping until they reach a melting point and then pressing them together to form a strong, permanent joint. The process creates a homogeneous bond that is as strong as the pipe itself and effectively minimizes the risk of leakage, which is critical for maintaining the integrity of pipelines in water distribution systems.

In contrast, the other types of joints mentioned do not typically apply to HDPE piping. Welded joints are more common in metal piping systems, where welds are used to bond metal pieces together. Screw joints typically involve threaded connections, which are not standard for HDPE due to the material's flexible nature and the risk of leaks if not properly connected. Compression joints, while sometimes used in plastic piping, generally do not provide the strength or durability needed for extensive HDPE piping systems compared to thermal butt-fusion. Thus, thermal butt-fusion stands out as the method that aligns best with the properties and requirements of HDPE piping.