You must clean an operating tank that is not internally coated and does not have a receiving filter separator every?

The correct answer reflects the recommended cleaning schedule for an operating tank that lacks internal coatings and does not have a receiving filter separator in place. Regular maintenance and cleaning of such tanks are crucial to prevent sediment buildup, microbial growth, and contamination of the fuel or water they store.

In this context, a cleaning interval of every four years is typically established to ensure the integrity and efficiency of the tank system. This frequency helps maintain optimal operating conditions and prolongs the lifespan of the tank while minimizing potential issues that could arise from neglecting proper maintenance.

The other intervals suggested do not align with established best practices for maintaining uncoated and unfiltered tanks, as longer durations would increase the risk of contamination and operational problems. Keeping to a four-year cleaning schedule supports safety and performance standards essential for effective water and fuel systems maintenance.