What is the recommended procedure for evacuating an underground tank?

The recommended procedure for evacuating an underground tank involves removing as much liquid as possible through the liquid withdrawal connection first. This method is effective because it ensures that the majority of the liquid propane is extracted from the tank systematically and safely, minimizing the risk of vapor release and potential safety hazards that can arise from improper handling of flammable materials.

By utilizing the liquid withdrawal connection, operators can maintain better control over the tank's contents, which is crucial for safety and compliance with environmental regulations. This approach also helps in preparing the tank for maintenance or decommissioning, ensuring that it is at a lower liquid level before further actions like purging or cleaning take place. This step is critical in managing the tank's contents safely and effectively.

Other options, such as using a siphoning method or filling the tank with water, are not standard practice for evacuating a propane tank and may introduce risks or complications that can be avoided.