Effects of low level magnetic and electromagnetic fields (below B similar to 100 mG for ac magnetic field, and below B similar to 1000 G for static magnetic field), on purified water that is in the process of equilibration, were investigated. The pH and oxidation-reduction potential (ORP) of distilled and deionized water, previously stored for air equilibration, were measured after exposure to magnetic fields (ac and dc) of different strengths. Readings showed slow and large fluctuations (similar to0.05-0.1 pH unit, similar to60 mV for ORP) during the first several hours. These readings looked deceptively stable due to the extreme slowness of the fluctuations. When readings were taken beyond this period, for days, the pH and ORP generally changed slowly toward equilibrium values in a quasi-linear fashion. They changed faster, on average, in those samples that had been exposed to higher magnetic fields. Readings in water samples often "got stuck", remaining unchanged over an extended period before starting to change again, when stored for equilibration with air and measured in a mu-metal shield, where the ac magnetic flux was similar to0 mG (zero field). These results indicate that, to accurately evaluate the effects of weak magnetic fields on water, subtle experimental conditions such as differential field conditions produced by common lab devices and procedures, and background lab fields, cannot be ignored. Moreover, extending measurements beyond several hours may be essential to reliably observe the presence or absence of these effects.