What is the primary function of a barometric loop in plumbing?

The primary function of a barometric loop in plumbing is to prevent back siphonage. A barometric loop is a vertical loop created in a piping system, which utilizes the principles of fluid mechanics to prevent contaminated water from being siphoned back into the potable water supply. The design of the loop creates a hydraulic barrier that prevents negative pressure, which could otherwise draw water backward through the system. When there is a drop in pressure in the supply line, the water in the barometric loop effectively acts as a seal, ensuring that contaminants cannot flow back into the drinking water system. This is crucial for maintaining the safety and quality of the potable water supply.

The other functions listed are not applicable to a barometric loop; it does not increase water pressure, support water expansion, or decrease flow rate, as its main focus is on preventing backflow and maintaining the integrity of drinking water systems.