UPDATE

I cleaned the cell today with the acid solution as recommended (4 parts water, 1 part muriatic acid: 4 cups water and 1 cup acid turned out to be just about the right amount to fill the T 15 cell). There didn't seem to be much bubbling, so I'm guessing there really wasn't much calcium on the cell plates. I checked the controller readings after reinstalling the cell and didn't notice anything different. I'll keep any eye on CL level to see if the cell is working more effectively or not (based on the unchanged controller readings, I suspect not).

I'll post an update once I see if the cell's efficiency has changed or not.

Thanks for all the feedback and help.

PS - Btw, I just dumped the used acid solution back into the pool.