The house I moved to 22 years ago had a pool and I have kept it up ever since. Up until 2 years ago I used a DE filter. The original owner was a do-it-yourself kind of guy and the filter just drained to the back of the cabana. So for 20 years i have been buying bags of DE and backwashing/draining to the back of the cabana having no idea that it could be a problem and there is a great amount of muddy DE far away in my back yard. My pool store guy told me that this is dangerous and I have to get rid of it. How dangerous is it and how should I get rid of it?