What causes there to be blood in stool when i go to flush?

Hemorrhoids: Moat common cause for painless bright red bleeding in the toilet bowl after a bowel movement is internal hemorrhoids.

Hemorrhoids: Although hemorrhoids is the most common, many other more serious causes exist. You don't mention your age or sex. Could be colitis, anal fissure, colon tumor among other things. Remember: no amount of rectal bleeding is normal or should be ignored. See your doctor and possibly a colorectal surgeon for a proper evaluation.