The red MSX source (RMS) survey has identified a large sample of candidate massive young stellar objects (MYSOs) and ultra compact (UC) HII regions from a sample of ~2000 MSX and 2MASS colour selected sources. To search for H_2_O masers towards a large sample of young high mass stars and to investigate the statistical correlation of H_2_O masers with the earliest stages of massive star formation. We have used the Mopra Radio telescope to make position-switched observations towards ~500 UCHII regions and MYSOs candidates identified from the RMS survey and located between 190{deg}<l<30{deg}. These observations have a 4{sigma} sensitivity of ~1Jy and a velocity resolution of ~0.4km/s.