Homeowner remodeling a bath which had the toilet on a raised platform about 7 inches above the floor. Took out the platform and now need to lower the toilet flange to sit on a tile floor to be installed. Plan is to cut off the old flange (and PVC pipe) to at least level with the floor line and install a new "inside pipe" flange which I bought at Home Depot. Problem is, when the floor was poured, cement around the pipe itself is actually built up above the floor level by maybe a half inch. Don't know why this was done, but it clearly makes it more difficult to lower the flange. So, my plan is to remove this "extra" concrete around the pipe with a power chisel, a drill-like tool that uses either drill bits or chisel blades in a "impact" mode. Now I know I shouldn't go crazy with this power, but I was wondering what are the chances that in removing this excess cement from around the pipe, I might crack the pipe and then really be in trouble. Or, is there a better way to chisel out excess cement from around the PVC pipe? Thanks, in advance for any ideas.