Toilet Flange, Toilet Flanges, Toilet leak at base, Leaky Toilet, Toilet Leaking, Install ToiletLeaky Toilet at the base is the # 1 service repair encountered by Mock Plumbing. A toilet flange is a device located between the toilet base and the floor. The water seal between the toilet and sewer piping is called Was Ring and it is placed on top of the flange. Two bolts are attached to the flange anchoring the toilet. Twist-n-set toilet flanges, as shown here, are used to replace damaged toilet flanges and can be used on both cast iron pipe and PVC. The flange is placed inside the pipe and tightened until the gasket expands and wedges tightly between the pipe and the flange.