Product review (5 stars): WF2 Filter discoloration
There have been numerous comments about concern because of discoloration and/or mold buildup on the filters. Some report this happens overnight! Discoloration and mold are not the fault of the filter, the filter is warning you that there is a problem in your water. You are apparently using water that contains high levels of iron in solution that causes the discoloration. If mold grows on the filter there is a very good chance that the water also contains iron bacteria. If this occurs, have your water tested specifically for levels of iron bacteria and don't drink the water until you have the results indicating iron bacteria is not present. National standards for potable water DO NOT require testing for iron bacteria; you must request the specific test for iron bacteria. You must have the water tested from your tap, not the water as it comes from your water department as the cause may be in your home's water pipes. (Are they from the era before plastic pipes? If so they are made of iron!)
I use my humidifier nightly for an average of 9 hours every night. They last approximately 3 months. I invert the filter once a week. They are always exactly the same color after 3 months of use when I replace the used filter with a new one. They are stiff from calcium accumulation. HAVE YOUR WATER TESTED!!!