What is the nominal water-containing capacity limit for a "Potable water heater" according to its definition?

The nominal water-containing capacity limit for a "potable water heater" is defined as 120 gallons. This specific capacity aligns with standards that categorize water heaters based on their size and functionality. A potable water heater is designed to heat water intended for human consumption, which includes household uses such as cooking, cleaning, and bathing.

Establishing a capacity limit helps ensure that the water heater meets certain safety and regulatory standards, particularly concerning pressure and temperature controls. Understanding this capacity is crucial for proper installation and compliance with plumbing codes, ensuring that the equipment operates safely and efficiently within its designed specifications.

Thus, the choice of 120 gallons reflects the standard used in the industry when categorizing potable water heaters, distinguishing them from larger storage tanks typically used for other heating purposes.