If a bottom feed water heater is used, what must the cold water connection have?

In the case of a bottom feed water heater, the cold water connection must have a vacuum relief in a vertical position to ensure safe and effective operation. A bottom feed system operates by drawing water from the bottom of the tank, which can create conditions that lead to negative pressure if there's a sudden drop in water usage or a leak in the system.

The vacuum relief valve allows air to enter the system when negative pressure is detected, preventing a vacuum from forming that could potentially collapse the tank or lead to improper functioning. This is particularly important in a bottom feed water heater since the design is focused on creating a steady flow of hot water while preventing air locks or negative pressure situations.

While a thermal expansion tank and a pressure relief valve are important components in a water heating system to manage pressure and thermal expansion, they do not directly address the need for preventing vacuum conditions specifically associated with bottom feed systems. A bayonet fitting pertains to specific structural connections but does not serve the purpose of managing vacuum conditions. Therefore, the requirement for a vacuum relief in a vertical position is crucial in maintaining the safety and efficiency of a bottom feed water heater.