Ways to unclog a ZeroWater filter include re-tightening the filter, punching holes into the screen of the filter and changing the water source. Make sure that the filter is truly clogged, as water filters slowly with a ZeroWater filter because it filters the water in five stages to increase purity.
The most common reason that ZeroWater filters get clogged is an airlock. To break an airlock, unscrew the filter and re-tighten it. Do this several times until the problem is solved. If the filter is still clogged, there may be an obstruction in the filter. Punch a few holes into the screen of the filter with tweezers or a similar tool.
If none of the previous methods work, the clog may be due turbidity in your water source. Turbidity is the presence of solids in the water including soils, algae and microbes. In this case, use other filtration methods such as cloth or sand filtration prior to filtering with ZeroWater. Having high turbidity in your water means you need to replace the ZeroWater filter more often and you may not be able to unclog it. Test the turbidity of the water to find out approximately how long the filter will last.