Low-mass stars form when gravitationally unstable clouds of gas and dust collapse under their own weight. After several millions of years, planets have merged around the newborn star. In our solar system, at least one planet harbors life and its surface is covered in water. Most of this water was formed early in the protostellar evolution, before the collapse of the cloud. Following the trail of water through the different stages of star formation is an integral task in astronomy and astrochemistry. The aim of this thesis is to investigate the origin of warm water emission lines in deeply-embedded low-mass protostars. The relative abundances of different isotopologues of water can be used to infer the amount of processing that water goes through before being incorporated into comets and asteroids. The amount of water relative to other species can shed light on their inter-dependence.