How can I figure out why my undersink water filter system is clogged?
If the filters are the twist-lock type (o-ring that tightens with a 1/4-turn)  they may not be fully seated into the filter port. Remove the filters and re-install them making sure to apply enough upward pressure to fully seat the filter. BTW: the Aqua-Pure web page will have this filter. Here is the link:  http://www.3m.com/3M/en_US/company-us/all-3m-products/~/3M-Aqua-Pure-Under-Sink-Water-Filtration-System-Model-AP-DWS1000-1-per-case-5583101?N=5002385+8709316+8709366+8710655+8710937+8711017+8711350+3294748997&amp;rt=rud