Description
Vents release air and are a dynamic and integral part of tank operation. The air pressure inside of a tank is always trying to equalize with the air pressure outside as the water level rises and falls in the tank. When the tank is filling with water, displaced air has less space and puts pressure on the tanks. The air is forced out of the tank through the vent and overflow as well, if it is not overflowing with water. When water is drawn out of the tank, the air has more space and creates a vacuum. Outside air is pulled into the tank through the vent and overflow. Thin walled metal tanks can be protected against excessive pressure and vacuum with a pressure/vacuum relief mechanism. Also, storage tank vents cannot serve as the overflow; tanks must have a vent separate from the overflow.