Water quality monitoring of distribution systems has traditionally relied on infrequent grab sampling and laboratory analysis, lacking spatiotemporal resolution to capture contamination events across complex water networks. However, emerging sensor technologies integrated into wireless sensor networks (WSNs) enable real-time continuous monitoring to revolutionize water security. This paper explores the development of affordable in-situ optical sensors leveraging UV–vis absorption and fluorescence measurement techniques for improved water quality monitoring in distribution systems. Critical considerations for designing a low-cost UV absorbance/fluorescence sensor are examined, including strategic photodetector selection using the technique for order of preference by similarity to ideal solution (TOPSIS) analysis and optimizing components through design of experiments. The impact of sample holder material, air gap, and water type are quantified, informing the prototyping process. Calibration with humic acid solutions demonstrates the sensor’s sensitivity across a wide concentration range. While challenges persist around sensor miniaturization, power management, data transmission, and cost-effective mass production, the outlined innovations illuminate opportunities for deploying spatially dense WSNs for real-time water quality monitoring. Continuous high-resolution data can revolutionize contamination detection, process control, and watershed management when coupled with analytics and decision support systems, fostering intelligent and responsive urban water infrastructure.