How to Clean Old Gas From a Tank

By Jaimie Zinski
old gas, your tank
gas tank image by Mat Hayward from

Gas tanks are found on many devices in your yard and garage---from your motorcycle to your lawn mower. Your gas-powered vehicles may need a new tank, or the tank may just be dirty and require a proper cleaning. It is possible to clean old, unwanted gas from your tanks without having to pay a mechanic to perform this simple procedure. All you will need are a few common tools.

Remove the tank from the vehicle with a screwdriver. Remove the hoses, gas cap and any other items that are on the unit.

Pour the remaining gas into a bucket. This gas can either be stored in a 5 gallon drum in your garage or contact your local environmental waste service department to learn where gasoline can be disposed of in your area.

Pour cool water into the tank until it is half full. Pour 1/2 gallon of Muriatic acid into the tank. Wear gloves, goggles and a long-sleeved shirt while handling the Muriatic acid because it is corrosive and will damage your skin and eyes.

Fill the rest of the tank up with warm water and seal any holes with duct tape. Do not seal the hole with metal because the Muriatic acid will break down the metal. Allow the mixture to remain for 2 to 3 hours.

Pour the liquid into a 5 gallon plastic container and dispose of it in the same fashion as you did the gasoline.

Rinse the tank out with cool water. You can utilize a garden hose to perform this. Make sure the water is running slowly so you do not splash any remaining acid onto your skin.

Allow the tank to dry. This could take several days, so do not disturb it or attempt to reuse the tank until it is completely dry. You can also prop the tank on one side and utilize a hair dryer to remove any excess water.