Broken resin will not backwash out of a system when it has a top screen, the top screen will keep it in and cause a layer of tightly packed broken resin beads to form a restricting layer on the top of the resin. I know many field technicians that have removed the top screen, and then increased the backwash rate to remove the broken resin beads from the system. BTW, this works, but is only temporary and should not be done. Resin is cheap and simple to replace. Be sure to inspect the top screen, clean it, and be sure to remove all of the old resin. It does not take much bad resin to cause the symptoms you are describing. Tom is absolutely correct, you should have been sold 10% crosslink resin which will last considerably longer than 8% in a chlorinated supply, I would highly recommend a carbon tank be installed ahead of your equipment. If the chlorine is bad enough to damage resin, how damaging is it to you when you are breathing it into your lungs in a hot, steamy shower?