fourth year
Unless you have your toilet sitting on one of the downspouts Sylvan mentioned, (which can also be 8″ or even 10″ depending on the installation, but irrelevent for your question), then you do not have 5″ or 6″ pipe. The hole in the flange is 5″ because it fits over a 4″ pipe which measures between 4 3/8 and 4 1/2″ outside diameter. It does not matter when the house was built, toilets have always been made to fit over a standard flange which would not be 5″. My original answer still holds. You have a 4″ flange designed to be lead/oakum sealed to a cast iron riser. If you have other than 4″ cast iron in the floor then you need a different type of flange.
