My mother has a well that is about 300 feet deep. IT has given her lots of trouble over the years. Now it seems that she is getting rust or sand in her filter. She changes the long woven filter about every two to three weeks and finds a lot of little rust like grains in the bottom . She was told that it was the casing and it needed to be replaced. That does not seem likely to me as the grains are pretty large and I do not see how they would go through the pump for so long and not destroy it. I do believe the casing has a crack or is broken somewhere. The well used to be much deeper but it was pulled up a couple of years ago and a new pump installed and they did not drop it as deep. I need some help as to where to start looking. She seldom uses the well for fear she will run out of water. Could it be the tank? It is most likely 15-20 years old.Thanks so much for the help.