Poor-quality

water-supply and sewage pipes

Much of Norway's water and sewage grids is in bad condition - and is getting worse.

This results in leaks in water-supply pipes and poorer water quality. Leaks in sewage pipes result in local contamination. For some years, SINTEF has been developing methods of determining the condition and expected development of condition of various types of pipe materials. These include both laboratory and field methods. This is an interdisciplinary project, in which metallurgists, experts on plastics and concrete, and water resources scientists are involved.

The need for maintenance and renewal is growing, and many local authorities face the necessity of making large investments in the near future. With limited resources available to local government, allocating priorities to renewal projects is an important task. In this connection, methods for the condition monitoring of pipelines are of great importance.

There are about 60,000 km of water and sewage pipes in Norway, some of which date back to about 1860. The cost of replacing all of these would be about NOK 100 billion.

One third of the water pipes are cast iron with no corrosion protection, and a large proportion of these is exposed to severe corrosion attacks. SINTEF has developed methods of analysing the corrosion condition of such pipelines and of calculating their expected remaining lifetime.

A further third of the water system consists of ductile cast iron pipes with an inner coating of concrete mortar. SINTEF is now studying samples of these pipes taken from the water supply grid.

The last third of Norway's water-supply grid, and a similar proportion of the sewage network, consist of plastic pipes. For many years, SINTEF has been responsible for checking the quality of new products for the plastics industry, and is now exploiting its experience and using the same methods to study the condition of pipes that have been in use. This type of study is not known to have taken place anywhere else.

Concrete is used for large-diameter water pipes and for sewage pipes, particularly storm water sewers.

A large-scale study of concrete sewage pipes shows that the quality of pipes that are more than 25 years old is unacceptable by current standards, but that a considerable improvement in production quality has taken place.