How to Safely Drain Your Gas Tank

Draining a Fuel Tank Safely

Martin Diebel/Getty Images

There are a number of reasons that you may find it necessary to drain all of the fuel out of your gas tank. The most common reason these days is bad gas. In the old days, "bad gas" meant fuel that was years old, contaminated with water, or was full of solid debris. It was rare to accidentally end up with bad gas in your fuel tank, although there were always reports floating around of people who filled their tank with bad gas right from the gas station's pump. But for the most part bad gas was a problem that affected people like farmers and antique car guys who let things sit for a long, long time then tried to take a shortcut by not cleaning the old fuel out of the tank or engine before they tried to bring some piece of internal combustion equipment back to life.

That was the old days. These days bad gas has become everyone's problem. The addition of Ethanol to automotive fuel has changed the gasoline game for the worse. Ethanol-enhanced fuel has been causing serious problems in both large and small engines. Where old, ethanol-free gas took years to become unusable, new E10 (10% ethanol) fuel can go bad in just a few months. This is a real problem. Check out this Consumer Reports article detailing some of their findings pertaining to E15 (15% ethanol mixture) gasoline.

Let's get back to talking about how to safely get bad gas out of your tank before you let it gum up your engine's works.

Choosing a Proper Gas Siphon

Hopkins 10803 FloTool Transfer Pump
This manual pump is approved for combustibles like gasoline. Hopkin 10803 FloTool From Amazon

When most people think about siphoning gas out of a car or truck's gas tank, an ugly picture comes to mind. They imagine themselves sucking on a long tube with one end shoved deep into the fuel filler hole of their vehicle, hoping they can get the tube out of their mouth and into a bucket before the gas hits their lips. While this method is tried and true, it's not at all clean, and not entirely safe. Fuel is very combustible, and you never know when something could spark a fire. Safety first, right? With a simple tube siphon, you run the risk of spilling gas all over, and this is a fire hazard. We recommend using a proper manual pump that is approved for combustible liquids like gasoline. If you go to the auto parts store you can find one, just be sure to look for the combustibles approval, because many siphon pumps are not suitable for fuel. I'd also stay away from the super-cheap versions that use a little bulb to start your siphone for you. I've had terrible luck with these. The equipment pictured above features a high volume hand pump which is completely sealed, and comes with lots of tubing for both the gas tank side and the end that will go into your approved fuel container.

Pumping the Gas Out of the Tank

Manual fuel pump in action
Pumping fuel out of the tank safely. photo by Matt Wright, 2012

Before you start pumping, be sure you are set up. You'll need to have an approved gasoline container handy to hold the gasoline. If your tank is full, you'll need more than one! Do the math before you start. Assemble your manual pump per the instructions, then insert the inlet hose into your gas filler hole. You'll have to move past the little metal flap most of the time, this is fine. Keep feeding the tube until you have only about 2 feet left hanging out of the tank. Now take the other end and insert it into the approved fuel container. The type of pump pictured doesn't need priming, so just start pumping until you feel gas flowing. That's it!

See the next page for a tip on finishing the job without incident!

Removing the Siphon Tube from the Gas Tank

Oleksiy Maksymenko/Getty Images

With all of the gas drained from your tank, you are ready to install your new fuel filter, or put in a new fuel sender, or just replace the entire fuel tank. But that tube seems to be stuck in your fuel filler! Don't start yanking on it. What has happened is the little metal flap that keeps fuel from splashing back has caught the tube like a fish hook. Push the tube back in a little, then hold the flap back with something while you slide the tube back. If you use a metal screwdrive, be sure to ground it against the car's structure before you touch the fuel filler with it to avoid sparks. Or better yet, use a wooden stick.