Quote Originally Posted by buzzhazzard
Consider having your pool water tested for phosphates. I was having the same problem last year and discovered my phosphates were very high. It took some work to get rid of them, but whereas last year I was running at 80% with very little production, this year I am running at about 20%.

Also, slightly loosen the union at the downstream side of the cell and collect the water while the cell is generating. Test that water and see what the Cl tests.
2 good points here. If phosphates are a limiting factor in algae growth in your pool you might always be fighting algae which can explain a high chlorine demand. However you would most likely be showing CC all the time.

Checking the water right after the cell will certainly tell you if it is working or not. It should be very high (use OTO to test since it doesn't bleach out)