Sorry just reading this, but can shed some light.
I had a new tank for softening, with a mediaguard (KDF55 Cartridge). Here's what happened next:
Started out great, but after a short while the water pressure started dropping off, got really poor. KDF cartridge was the problem. Here's how I fixed it:
I started over. Put the riser tube, new rock bed, 20lb of KDF, followed by coconut charcoal, then resin. My water pressure is like new.
But here is the kicker... When I opened the KDF cartridge to maybe use some of the stated "4lb of KDF", what I found was a lot of carbon, and very little KDF. So when I addressesd this issue with PROCAN up in Canada, they manufacture the KDF MEDIAGUARD, they would not reply.
So what I am telling you:
If you want the benefits of KDF, then put it right into the tank. remember, it is the heaviest of the 3 items I used. so, during regen. it all gets rinsed, and cleaned, then the KDF goes back to the bottom where it belongs. No more water pressure restrictions. the water is awesome with 20lb of KDF, no "****" is getting through!
hope this helps ... Fred firstname.lastname@example.org