What is commonly used to seal threaded joints in plumbing systems?

In plumbing systems, the most commonly used method to seal threaded joints is with joint compound. Joint compound, sometimes referred to as pipe dope, is a thick paste that helps to create a watertight seal between the threads of two mating pipes. When applied to the threads before making the connection, it fills in any small gaps and imperfections that might otherwise allow water to leak through, ensuring that the joint is secure and prevents any leakage.

The effectiveness of joint compound lies in its ability to both lubricate the threads to ease installation and to provide a strong seal against pressure and temperature changes within the plumbing system. This makes it particularly suitable for both metal and plastic pipes, enhancing the integrity of the joint under various service conditions.

Additionally, sealant tape is also a common sealing method, specifically for certain applications, but joint compound tends to be preferred for more robust sealing requirements, especially in high-pressure systems. Adhesives and thread lubricants serve different purposes and are not primarily intended for sealing threaded joints in plumbing.