What is a common material used for sealing joints in copper piping?

Lead-based solder is commonly used for sealing joints in copper piping due to its ability to create a strong, durable bond that can withstand the pressure and temperature changes typical in plumbing applications. When copper pipes are fitted together, the solder melts and flows into the joint, filling any gaps and ensuring a watertight seal as it cools and solidifies. This method has been traditionally favored because it’s effective in joining two pieces of copper securely, which is crucial for maintaining system integrity.

While alternatives like plastic, silicone, or metal clamps may be used in specific situations or modern plumbing practices, lead-based solder has been a standard in traditional systems. However, it's important to note that due to health concerns associated with lead, its usage has been reduced and regulated in many areas; thus, many modern applications now use lead-free solder or other compounds.