Connect a hose to the open valve in order to direct the water to a location where it will not cause any localized flooding or erosion. Permanent water tanks have a washout valve that is located at the base of the tank. If your water tank is permanent and contains a washout valve, use this to drain the tank instead of the regular outlet valve or tap.
Use a wet/dry vacuum to suck up any water that remains. If you have a small tank and can safely tip it up, you can do this to drain any remaining water from the tank. Once you’ve got all but a very small amount of water out of the tank, you can use towels to soak up any water that remains.
You may need to use a brush with a long handle, depending on the size of your tank. This type of brush may be more difficult to maneuver, but will allow you to reach the bottom of the tank safely. If you’re using a long-handled brush, you’ll probably need to move the brush up and down vertically instead of horizontally. [3] X Research source Avoid brushes with steel bristles or sponges made of steel. Plastic can scratch easily and these materials will probably be too harsh for a plastic tank.
Fill your power washer with water or cleaning solution. Start by holding it about four feet away from the surface you’re cleaning. Move closer until you find the distance that works best for removing dirt, sediment, and debris. Hold the pressure washer so the water hits the interior wall of the tank at a 45 degree angle. Continue this until you are satisfied that you’ve removed all the dirt and sludge from the walls of your tank. Pressure washers are very powerful, so always wear safety goggles when you’re using them, never point them at another person or animal, and follow all other safety regulations. It is also a good idea to have someone with knowledge of power washers give you a lesson on starting and using them before using yours. [5] X Research source
Alternatively, you can rinse the tank by filling it with hot water and letting it stand for several hours. Drain the tank, making sure you collect and safely dispose of the drained water. Repeat this process until the water is completely free of detergent and sediment.
After vacuuming, you may need to take a clean rag or mop head and run it along the bottom of your tank to clean any areas that still have sediment on them.
For a 250 gallon tank, use 4 cups of bleach. For a 500 gallon tank, use ½ gallon of bleach. For a 750 gallon tank, use ¾ gallon of bleach. For a 1,000 gallon tank, use 1 gallon of bleach.
Remove any remaining liquid by scooping it out with a bucket and then using towels, a clean mop head, or a wet/dry vacuum to pick up the rest.
