The unique patented Qwik System Flush® formulation has been specifically engineered to remove moisture and acid while other flushing agents do not remove these impurities. However, the ability of Qwik System Flush® to absorb and remove moisture from surfaces of a system being cleaned, also means that the Qwik System Flush® will absorb moisture from the air, if left exposed to the air. Once an unpressurized can of liquid flush is opened and partially used, air enters the can to replace the volume of flush that was used. Ambient air is loaded with moisture, and if the flushing compound was designed to absorb moisture, the flushing compound left in the can would become saturated with moisture.
Clearly the moisture absorbed from being exposed to air reduces the effectiveness of the remaining flush, and using a flushing agent that is saturated with moisture could actually add moisture to the system, rather than remove it! This is of course not a problem in the pressurized aerosol Qwik System Flush® can because the Qwik System Flush® is never exposed to air, except after the flushing process is completed.