The recent development of the International Global Navigation Satellite Systems Service Real‐Time Pilot Project and the enormous progress in precise point positioning (PPP) techniques provide a promising opportunity for real‐time determination of Integrated Water Vapor (IWV) using GPS ground networks for various geodetic and meteorological applications. In this study, we develop a new real‐time GPS water vapor processing system based on the PPP ambiguity fixing technique with real‐time satellite orbit, clock, and phase delay corrections. We demonstrate the performance of the new real‐time water vapor estimates using the currently operationally used near‐real‐time GPS atmospheric data and collocated microwave radiometer measurements as an independent reference. The results show that an accuracy of 1.0 ~ 2.0 mm is achievable for the new real‐time GPS based IWV value. Data of such accuracy might be highly valuable for time‐critical geodetic (positioning) and meteorological applications. Key Points We develop a new RT GPS water vapor processing system PPP ambiguity fixing with RT satellite orbit, clock, and phase delays Our results are very promising and demonstrate RT ZTD/IWV accuracy