The accuracy of estimated Precipitable Water Vapor (PWV) content in near real time using ground based GPS/Met strongly depends on the quality of GPS orbits. The impact of the predicted GPS orbits in IGS Ultra-rapid products on PWV estimation is investigated in this paper. A few satellites of poor orbits will contaminate the estimated PWV. In this study, variance ratios derived from adjusted GPS double difference carrier phase observations for different satellites are used to identify poor GPS orbits. By excluding or down weighting the measurements related to those poor satellites, the accuracy of PWV estimation can be significantly improved.