How many inches above the flood rim must a hose bib be installed?

A hose bib must be installed at least 12 inches above the flood rim to ensure that it is protected from potential backflow and contamination. The flood rim of a fixture is the highest point at which water can rise before it overflows. Installing the hose bib at this height creates a critical air gap, which prevents any possible backflow from entering the potable water supply, especially in situations where the hose might be submerged in water, like in a garden or during washing. This requirement aligns with safety regulations to maintain the integrity of the drinking water system.

Additionally, 18 inches or higher may be more protective in some scenarios, but the minimum requirement according to the Massachusetts Plumbing Code is indeed 12 inches. Installing it flush with the flood rim would not provide sufficient protection against contamination, and placing it lower than 12 inches could lead to unsafe conditions.