Ensuring access to good quality water is crucial for sustainable development, particularly in developing nations. However, the lack of affordable and reliable solutions for monitoring water quality remains a significant challenge that the LOTUS sensor meets: it is a compact and versatile multiparametric sensor designed for real-time monitoring of chlorine, pH, temperature, and conductivity in potable water. The proposed solution features a cylinder-like structure, measuring 21 cm long and 3.5 cm in diameter. It integrates temperature sensors, conductivity sensors, and a 2x10 sensor array of multi-walled carbon nanotube (CNT) chemistors. The CNTs, arranged in random networks between interdigitated electrodes, can remain non-functionalized or be functionalized with a dedicated polymer to modulate their sensitivity. Six LOTUS sensors were tested in a 44m-long water loop under a flow rate of 0.3m/s and pressure of 1 bar to evaluate the system performance. To manage the high noise levels caused by strong electromagnetic interferences in the facility, particularly under flowing water conditions, a strong effort was put into data denoising techniques. After extensive denoising and calibration model optimization, temperature, conductivity, chlorine, and pH estimation were achieved with mean absolute error (MAE) as low as 0.34oC,73.2μS/cm,0.13mg/L and 0.12 pH unit in flowing water (achieved on different sensors due to dataset limitations). Notably, the dataset also demonstrates the role of CNT functionalization in chemical sensing, with the selected polymer modulating the sensitivity to pH by 50%.