Before starting, ensure the tank is properly prepared. First, shut off the dispenser's power supply to eliminate electrical hazards. Then, drain the remaining fuel from the tank using the dispenser's built-in drainage system or a dedicated transfer pump, directing the fuel to a clean, approved storage container for temporary holding.

This step not only makes cleaning safer but also prevents fuel from mixing with cleaning agents, which could contaminate the fuel or damage the tank. Once drained, open the tank's access hatch or manway to allow proper ventilation, reducing the concentration of flammable vapors inside the tank—never clean a closed or poorly ventilated tank.

Next, remove loose debris and sediment from the tank's interior. Use a soft-bristled brush or a low-pressure vacuum designed for hazardous environments to gently sweep or suction away dirt, rust flakes, or fuel residues that have settled at the bottom of the tank.

Avoid using hard or abrasive tools, as these can scratch the tank's inner surface (especially critical for coated mild steel or HDPE tanks) and create areas prone to future corrosion or fuel contamination. For stubborn residues, dampen a lint-free cloth with a mild, fuel-compatible cleaning solution—avoid harsh chemicals that could degrade the tank material—and wipe the affected areas carefully.

After removing debris, rinse the tank's interior to eliminate any remaining cleaning solution or fine particles. Use clean, filtered water (for metal tanks) or a fuel-compatible rinsing agent (for HDPE tanks, if needed) and spray the interior surfaces evenly.

Allow the rinsing liquid to drain completely through the tank's drainage system, ensuring no moisture is left behind—residual water can cause rust in metal tanks or mix with fuel to form sludge. For thorough drying, leave the tank's access hatch open and use a portable fan (approved for hazardous areas) to circulate air inside until the interior is completely dry.

Finally, perform a post-cleaning inspection and reassembly. Check the tank's interior for signs of damage, such as cracks, peeling coatings, or corrosion, and address any issues before refueling. Inspect the tank's gaskets and seals around the access hatch to ensure they are intact and create a tight seal.

Once the tank is deemed clean and undamaged, close the access hatch securely, reconnect the fuel lines, and refill the tank with clean fuel from a trusted source. Restore power to the dispenser and run a test refueling cycle to confirm the system is working properly.