This is an old thread but I'm having the same problem. This is an amazing site and I'm hoping that someone can help me.
After some neglect, we realized that our backflushing AN had used up all its material (probably a year). The Culligan man came and put two bags of calcite in it. About one week later, our sewer pipe stopped working. Opening it up, it was clogged with white particles that look just like the calcite. I came to this forum and figured that the Culligan man must not have done the backwash and didn't slowly increase the water pressure afterwards, as suggested here.
So, after cleaning out the sewer pipe, I put in another 1/2 bag of neutralizer (the AN was mostly empty, so it must have been the calcite that was backflushed into the sewer pipe). I believe I followed the instructions here. I did a slow backwash, running water at 1/4 full, and watched the drain line for material. I didn't see any. I thought I had fixed it.
Five weeks later, the sewer pipe clogged again. I took it apart and it was the same reason as before. It appears to be the calcite material.
What could be the cause here? The AN is a Culligan, with the Mark 812 tank. That is an old system, but the tank (must have been refurbished) was only installed in 2013 according to Culligan's records.
Would there be some problem with the AN that would be causing this issue? The Culligan man suggested we might want to rebed the AN next summer, but I don't see anything on the internet saying this would cause the loss of material.
After the AN, we have a Culligan Softminder Twin. I don't believe there is a problem with the water softener, but the drainage tubes of the AN connects to the drainage tube of the water softener in a T connection, before entering the sewer line. Is there any chance that the water softener backflush could be drawing media out of the AN, particularly if they are both backflushing at the same time.
Thank you in advance for any suggestions or ideas.