This section discusses the advantages and approach to performing skeletonization using Skelebrator.

Series pipe removal, also known as intermediate node removal or pipe merging, is the next skeletonization technique. It works by removing nodes that have only two adjacent pipes and merging these pipes into a single one. As with Branch trimming, any demands associated with the junctions being removed must be reallocated to nearby nodes, and generally a number of strategies for this allocation can be specified.

An evenly-distributed strategy divides the demand equally between the two end nodes of the newly merged pipe. A distance-weighted technique divides the demands between the two end nodes based on their proximity to the node being removed. These strategies can be somewhat limiting, and maintaining an acceptable level of network hydraulic precision while removing nodes and merging pipes is made more difficult with this restrictive range of choices.

Other criteria are also used to set the allowable tolerances for relative differences in the attributes of adjacent pipes and nodes. For example, an important consideration is the elevation difference between nodes along a pipe-merge candidate. If the junctions mark critical elevation information, this elevation (and by extension, pressure) data would be lost if this node attribute is not accounted for when the pipes are merged.

Another set of criteria would include pipe attributes. This information is needed to prevent pipes that are too different (as defined by the tolerance settings) hydraulically from being merged. It is important to compare certain pipe attributes before merging them to ensure that the hydraulic behavior will approximate the conditions before the merge. However, requiring that pipes have exactly matching criteria limits the number of elements that could potentially be removed, thus reducing the level of skeletonization that is possible.

In other words, although it is desirable for potential pipe merge candidates to have similar hydraulic attributes, substantial skeletonization is difficult to achieve if there are even very slight variances between the hydraulic attributes of the pipes, since an exact match is required. This process is, however, very good at merging pipes whose adjacent nodes have no demand and that have exactly the same attributes. Removing these zero-demand junctions and merging the corresponding pipes has no effect on the model's hydraulics, except for loss of pressure information at the removed junctions.

Series pipe removal is called Series Pipe Merging in Skelebrator.