What is the minimum size air gap required?

The minimum size air gap required according to plumbing codes is typically twice the size of the drain. This is vital for preventing backflow and ensuring that wastewater does not contaminate the clean water supply. The air gap acts as a physical barrier, allowing air to break the syphon effect, which can create a pathway for contaminants to enter the potable water system.

Using an air gap of at least double the diameter of the drain helps provide a sufficient buffer zone to minimize the risk of any possible backflow or siphonage. This specific measurement supports safety regulations that aim to protect public health by avoiding situations where bacteria or other harmful substances could travel back into clean water lines.

It's important to ensure compliance with these guidelines, as they form part of the health and safety regulations laid out in the Massachusetts Plumbing Code.