To provide a firm foundation for the tank, what type of material should be used as a bed?

For establishing a firm foundation for a tank, the use of aggregate is ideal. Aggregate is characterized by its ability to provide excellent drainage and support, making it a suitable choice for bedding material. Its composition typically includes a mixture of different sizes of stones, which can effectively distribute the weight of the tank and maintain stability. This property helps minimize settlement or shifting over time.

Sand and gravel can also be used but are less favorable compared to aggregate in some installations. Sand may compress and create gaps under the tank over time, while gravel typically has larger particles that might move or shift, leading to instability. Properly graded aggregate provides a more uniform support structure, which is crucial for preventing tank deformation or failure, ensuring longevity and safety in fuel storage systems. Therefore, choosing aggregate for the bedding of a tank is the best practice in installation and retrofit scenarios.