Longevity

There are two elements of an above ground drainage system that should be designed and specified to last the lifetime of the building: 1. the internal rainwater pipes 2. the soil discharge stacks. Even when a building is modernised every 15 or 20 years, these elements along with the structure will likely remain. If the toilet or kitchen area is refurbished, the branch discharge pipes will often be renewed and therefore it may be appropriate to specify other materials for that element. But if the main stacks are to be specified to last the lifetime of a building, perhaps 50-70 years or more, the appropriate material is mechanical jointed cast iron, for it is one of the few materials you can reasonably fit and forget, as recognised by specifiers on many of the new PFI-type projects.