The Red MSX Source (RMS) survey has identified a sample of ~1200 massive young stellar objects (MYSOs), compact and ultra-compact HII regions from a sample of ~2000 MSX and Two Micron All Sky Survey (2MASS) colour-selected sources. We have used the 100-m Green Bank Telescope to search for 22-24GHz water maser and ammonia (1,1), (2,2) and (3,3) emission towards ~600 RMS sources located within the northern Galactic plane. We have identified 308 H_2_O masers which corresponds to an overall detection rate of ~50 per cent. We find no significant difference in the detection rate for HII regions and MYSOs which would suggest that the conditions required to produce maser emission are equally likely in both phases. Comparing the detection rates as a function of luminosity, we find the H_2_O detection rate has a positive dependence on the source luminosity, with the detection rate increasing with increasing luminosity.