How far above the flood level rim of the highest fixture must a stack type air admittance valve be located?

The correct response indicates that a stack-type air admittance valve must be located at least 6 inches above the flood level rim of the highest fixture. This height requirement is crucial to ensure proper functioning of the air admittance valve and to prevent any potential backflow of wastewater into the valve.

Being positioned above the flood level rim helps maintain the necessary air pressure in the plumbing system, allowing waste and venting to operate effectively. The distance acts as a safety measure to ensure that the valve remains unaffected by any potential overflows from fixtures, promoting a hygienic and efficient drainage system. This consideration is vital for preventing odors and maintaining the integrity of plumbing systems in residential or commercial installations.