I had a 4 stage (two pre filters, RO membrane and post filter) installed in my basement in December 2005, but a local company that went out of business about a year ago. I have replaced the pre-filters several times, with the following:
Sediment pre-filter with Pentek C1
Carbon pre-filter with Matrikx CTO/2// 32-250-125-975
I did this in September 2007, January 2009, July 2009, and again in May 2010. In May 2010 the system had slowed down noticeably, and when I changed the filters, there was a bunch of brown gunk in them, for the first time. Maybe 4 to 6 ounces in the first, and less in the second filter. When I changed them the system flowed fast again.
Now, two months later, the system is very slow, and so I changed them again (bought sets of two). There was some brown gunk, but not as much as the last time. System is still slow after changing them.
I think it is time to change RO Membrane and post filter, but I am not sure what to buy since no brand name or numbers are on the outside. If I take the membrane out of the system will it have numbers, or if I send a digital picture could I maybe get somebody to advise on correct membrane?