A water quality model (WQM) is a tool used for the prediction of water quality in a water distribution network. Previous studies have proposed a variety of methods for computing WQMs. All of these are flow-based and thus require the use of a hydraulic model. The current paper proposes a new methodology for a WQM based on a statistical approach. The study suggests a methodology that predicts the change in both detention time and water quality between two locations in a branched network, without the use of a hydraulic model. The methodology was implemented at a large water utility and tested using real-time data. The model output was then examined and verified by conducting a statistical test to compare the detention time with that predicted using an existing hydraulic model. It was found that the proposed model can be effectively used as a WQM.