A flush pump feature on a liquid purifying filter includes a segment of flexible tubing containing a small bulb pump is described. Two check valves are positioned upstream and downstream of the bulb pump which then terminates with a simple manually operated open/closed valve. The addition of this flush pump feature enables the filter unit to be easily purged of air at first use and also will make the filter easier to clean and maintain without the need to remove it from a hydration carrier. In addition, the flush bulb feature can also be used to perform a simple visual integrity test of filter while out in a remote location and also can be used to effectively remove bulk water from the filter for lighter storage when not in use which also minimizes freeze related damage when used in a cold environment.