Little Giant Pump GPH Dropping


Little Giant owners, <P>
My 2-MDQX-SC seems to have suddenly dropped by ~half the output in recent weeks. I performed my usual ~10 month maintenance in taking the impellar, ceramic shaft and nuts apart to be cleaned, along with scrapping the calcium carbonate buildup out of it. No change! I also took apart all the piping and didn't find any blockage. It seems to be the pump.<p>
What is your observed lifetime for these pumps?
Do you take apart the magnetic assembly to clean?
Any suggestions would be greatly appreciated.
Does anyone know where I can get a replacement 0-ring at a good price?<p>