Insight into connecting pipes

Significant importance of connecting pipes

The transport and distribution network of the Dutch water utilities covers a total length of some 130,000 kilometres. About half of that consists of connecting pipes with an average length of 8 metres. There are 8,429,000 administrative connections in the Netherlands, and 1,473,000 at the De Watergroep in Flanders. These are large numbers and that also applies to the economic value of connection pipes. Assuming an average replacement value of 1,000 euros per connection, the total replacement volume in the Netherlands amounts to 8.5 billion euros. This corresponds to one-third of the estimated replacement value for the transport and distribution network. Given this importance, a clear picture is needed of the condition, failure probability and residual lifespan of connecting pipes. But it has emerged that this clear picture is lacking.

Knowledge and recommendations

The aim of this project is to bring together the existing knowledge about connection pipes, to identify knowledge gaps and to make recommendations for effective and efficient follow-up actions.

This demand comes from the collective water sector research programme (BTO), which has been organising research on the condition, failure probability and residual lifespan of transport and distribution pipelines for several years. These issues have received limited attention until now as far as connection pipes are concerned. And it has been seen in practice that many replacement operations for these pipes are relatively late. Accordingly, the BTO Six-Year Distribution Plan is raising the question of whether enough attention is being paid to the rationale for decision-making about asset management in the field of connection pipes. This is quite a challenge because there is no uniform registration of malfunctions, and there is a wide variety of materials, diameters and design.

A first step on the road to establishing the basis required is to generate more knowledge about the service life of connecting pipes. Expert knowledge must also be collected and it will be necessary to analyse the existing data (including malfunction data) relating to connection pipes. To get to that point, research is being conducted into the possibility of splitting up connection pipes into cohorts, with a classification based on technical lifespan in line with the triangular establishment of cohorts for transport and distribution pipes that was developed successfully in the past. The allocation of these pipes to 22 cohorts, with the corresponding predictions of technical lifespan, will be used in a range of tools and methodologies to inform replacement decisions. On the basis of the findings, recommendations will be made in order to establish targeted knowledge acquisition for improved decision-making about replacing connection pipes.

Cohorts for technical lifespan

If it turns out to be possible and feasible – as in the case of transport and distribution pipes – to establish a classification in cohorts, and the corresponding estimation of the technical lifespan for connection pipes as well, drinking water companies can initiate the subsequent steps. They can make a broad estimate of the replacement work required for these connection pipes. It will then be desirable to establish knowledge rules for assessing specific replacement projects, with detailed rules at the street level.