Diverticulitis, drain tube placed on pelvic, gets 5ml/24h gray foul smelling fluid. is safe to remove drain tube? what is this fluid?

Do not remove: You likely had an infection due to a diverticulum rupturing, causing localized peritonitis and then abscess. Treatment for this is drainage and antibiotics until the abscess and inflammation resolves. Taking the tube out too early can cause reaccumulation of pus. See a colorectal surgeon following resolution to see whether you should have follow up surgery to removed the diseased segment.