How to Clean a Furnace Oil Tank
- 1). Place a bucket large enough to catch the fuel from the tank under its drainage valve. Open the drainage valve and let the contents of the fuel spill into the bucket. When the tank is empty, hook a garden hose to the valve and turn it on. Allow the tank to fill with water and drain it. Repeat until the water runs out clear.
- 2). Refill the tank with water once more, adding 1 cup of TSP for every five gallons of water held in the furnace oil tank. Open the main filler valve and put an air hose attached to an air compressor into the tank. Turn on the air compressor to agitate and mix the water/TSP solution. Let the compressor run for 10 to 12 hours. Then, remove the air hose and drain the tank.
- 3). Keep the drainage valve off once empty and put the garden hose into the main filler valve. Rinse the tank clean of TSP. Replace the drainage valve and remove the garden hose.
- 4). Pour 2 to 4 gallons of denatured alcohol into your tank. Let stand for six to eight hours to absorb any water remnants. Open the drain valve and let the denatured alcohol run out. Put the air hose back into the filler valve and blow out the inside of the tank. Refill the tank with fuel once completely dry.
Source...