Hi I am installing a D.E. Filter (Hayward) for my above ground pool. Can I use food grade D.E. in it? It is a more pure, more expensive D.E. than pool D.E..

Yes but you have to remember that the finer the grade of DE the more particals may come into your pool at first (will make pool cloudy and particals will lay on pool bottom). You really don't have to go with the higher grade and actually the Hayward filter will work better with pool grade. Please remember that DE is a cancer causting agent and try not to breath in the dust, and keep any small children away when you are doing this.