In 1981 - 1982 years it was revealed several Flashes of maser radiation of H2O radioline at wavelength 1.35 cm in the radio-sourse W49, developing practically synchronously at several radial velocities. It's known that components of the maser radiation of H2O radioline profile with different radial velocities arise in separate spatially diverse areas of a starformation. In such case our data show, that flash activity of H2O masers is determined by the external reasons - most likely because of change radiations of common "pumping" of maser sources.