I noticed few weeks back my ALK dropped from 9 to 6.7. I tested several times even ordering a new reagent. It still was low so slowly increased ALK dosage with the doser to an additional 50% and still was low. This was done over a few weeks. Today I decided to check the doser and make sure it was working and discovered the output tube was clogged and not dosing the right amount. I was aunable to clean the tube so replaced it. Guess I will have to check this every few months now. I did reduce the dosage back to the original volume.