When connecting lead pipes in a plumbing installation, what method is typically used?

In plumbing installations involving lead pipes, the typical method used is to join the pipe sections by melting the ends. This process, often referred to as "soldering," involves heating the lead until it reaches a molten state, allowing the ends of the pipes to fuse together as the lead cools and solidifies. This method ensures a tight and secure connection capable of withstanding the pressure of the water flowing through the pipes.

The other methods mentioned are less suitable for lead pipes. For example, welding is more commonly used for materials that can withstand high temperatures and are designed for structural integrity, which is not the case with lead. Using adhesive would not provide a reliable or durable connection in a plumbing context, as adhesives typically do not hold up against the pressures and environmental factors in plumbing systems. Threading, although a common practice in joining certain types of metal pipes, does not apply to lead due to its softness and tendency to deform, which could result in unreliable joints.