The life span of a drainage pipe of cast iron is determined by the interior corrosion. In a project executed at KIMAB, Europe’s leading corrosion and metal research institute, the result shows that the pipes can have a significantly shorter life span than what was formerly believed. In general, it has been said that cast iron drainpipes have a life span of around 50 years. Jörgen Almqvist from KIMAB doesn’t agree:

“Based on my experience and statistics from the projects I have worked on, you can establish that cast iron pipes, or gray pipes, have a much shorter life span than that.” says Jörgen.

In the Study that KIMAB undertook, there could be up to 20 years’ difference in the life span of the pipes in the same building. The horizontal kitchen pipes had the shortest life span, and the pipe parts that survived best over time were the vertical bathroom pipes. An average life span of cast iron pipes is thus closer to 40 years, and the kitchen pipes were worn out already after 30 years.

The study shows that the attack of corrosion varies greatly between different kinds of pipes and different parts of the same pipe. Among other things it was found that the vertical pipes in the kitchen were in much worse shape than the bathroom pipes. This was not only because the kitchen pipes experienced a higher frequency of rinsing, but also because a more agressive water passed through them, where pieces of food and fat create a build-up that can retain moisture and chlorides.

The life span is therefore to a large extent dependent on how the pipes are used, both in terms of frequency and of what is rinsed down them.                                                  

“My recommendation is that when the drainpipes get close to 30 years old, they should be inspected and repairs should be considered instead of being forced to take severe measures when a leak occurs. Our results show that there is a large need for maintenance in the drainpipes of buildings from the 1960’s and 1970’s, that is those that were installed during the Million Program,”
Jörgen concludes.