Jernrør

Jernrør, or iron pipes, refer to pipes made from iron, historically used in plumbing, drainage, and gas distribution. In many Nordic and European contexts, jernrør denotes pipes of cast iron or wrought iron that were installed in buildings and public utilities from the 19th through mid-20th centuries. Cast iron became the dominant material for water mains and sewers, while wrought iron was used earlier in some installations. Over time, iron pipes were often cement- or linings-lined to reduce corrosion and improve flow; joints were sealed with lead, oakum, or later with elastomeric gaskets.

Manufacture and joining: Cast iron pipes are manufactured by pouring molten iron into sand molds to form standard-length sections, which were designed to interlock via hubs or bells. Interiors were frequently cement-lined for protection in water systems. Wrought iron pipes were produced by forming iron sheet into seamless or welded tubes and joining sections with riveted or screwed couplings. In later periods, mechanical couplings and rubber gaskets replaced some traditional joint methods.

Performance and limitations: Iron pipes are strong and rigid, capable of withstanding substantial internal pressures in supply networks, but they are heavy and can be brittle if strained. They are susceptible to corrosion, depending on water chemistry and soil conditions, which can lead to leaks and reduced diameter over time. Service life varies widely, often several decades to a century in favorable conditions, but rehabilitation may be required as systems age.

Modern context: Many new installations use ductile iron, steel, plastics (PVC, HDPE), or composites. In existing older systems, jernrør may still be in service, or have been partially replaced or lined. Proper assessment by a qualified professional is advised for repair or replacement.