The dynamic properties of district heating (DH) networks include water flow and propagation of heat from production plants to consumers. Mathematical models of such networks can be applied. either for general understanding of DH systems, or in combination with production planning and optimization. One type of mathematical model involves a full physical modeling of the network, taking into account individual pipes, dimensions, material properties etc. Such full models tend to be computationally intensive when applied in network simulations, which can be a problem when considering large DH systems. In the current paper, a method is presented in which a fully described model of a DH network is replaced by a simplified one, with the purpose of reducing simulation time. This simplified model is generated by gradually reducing the topological complexity of the original network. The method is validated by applying it on a real case study, in which a network with over 1000 pipes is reduced to less than 10 pipes. The results show that such relatively simple networks can maintain most of the dynamic characteristics of the original networks.