The longitudinal seams of Roman waterpipes were made of lead: these were examined at different places. The seams were closed and tightened by lead, containing small amounts of tin, that is by a process of welding. The connection of two pipes was done in one case by welding two sheets of metal before shaping the pipe, in another case by overlapping the pipes and tightening them by a lead-tin alloy, a method which Pliny had mentioned.