I've been caring for this pool for 2 years. I know when its time to back wash by the spa over flow (and of course I monitor my pressure) I have been back washing and the sand filter pressure is not going down!! I used your method to clean my sand (no change). I do use my chlorinator and I took out all of the tablets and cleaned the grill. there were some small broken pieces down in the bottom. What should I be looking for?