What is the purpose of having a screen over the vent of a potable water tank?

The purpose of having a screen over the vent of a potable water tank is to keep insects from entering. This is crucial for maintaining the safety and cleanliness of the water supply. An open vent could allow insects and other contaminants to enter the tank, which can lead to water quality issues and potential health hazards. The screen acts as a barrier while still allowing air to flow in and out of the tank, which is necessary for proper ventilation and to prevent the creation of a vacuum that could impair water flow.

While regulating water flow, maintaining pressure, and preventing evaporation are important considerations in tank design and operation, they do not specifically address the primary role of the screen over the vent, which is focused on preventing unwanted organisms from compromising the potable water.