How to Siphon Gas

Co-authored by Matthew Rava

Last Updated: September 25, 2024 Fact Checked

Believe it or not, knowing how to siphon gas isn't just for petty criminals! This skill can be handy in all sorts of situations, whether you run out of gas miles from civilization, need to winterize a vehicle, or simply want to refill your lawnmower without having to make a trip to the gas station. Start with Step 1 below to learn how to siphon gas with nothing more than a length or two of plastic tubing and an empty gas can. Note: These methods may not work on gas tanks with special anti-siphon barriers (though such barriers can sometimes be held open with a screwdriver).

Method 1

Method 1 of 3:

Siphoning by Creating Pressure in the Tank

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Find a gas can or another closed container to siphon the gas into. Any standard gas canister of sufficient volume will suffice, provided the container is a closed one. Because gasoline fumes can be hazardous to your health and because you never want to risk spilling gasoline, it's usually unwise or even dangerous to transport gas in a bucket or other open container.^{[1]
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Find or purchase clear plastic tubing 1 inch (2.5 cm) in diameter. Siphoning involves sucking gas through a tube or hose into its new container. Clear tubing is desirable because it allows you to see the gasoline move through the tube, but, because this particular method doesn't carry any risk of gasoline getting in your mouth, opaque tubing will do in a pinch.^{[2]
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- For this method, you'll want two lengths of tubing - one long enough to reach deep into the gas tank and another, shorter length of tubing that will reach just inside the tank. Either obtain two separate lengths of tubing or cut one length of tubing to make two smaller lengths - the effect is the same.
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Siphoning works because of gravity - once you get gas flowing through the tube, it will naturally continue flowing as long as you keep the tube lower than the level of gas in the tank. Because of this, it's usually convenient to just put your gas can or receptacle on the ground under the tank.^{[3]
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Push the longer length of tubing well into the gas tank (keeping the other end in your empty gas can). The end of this tubing needs to be fully submerged in the gasoline in the tank - since you can't see where the end of the tubing is, you can check by carefully (so as not to inhale fumes) blowing into the tube and listening for the sound of bubbles. Push the shorter length of tube just a few inches into the tank so that both tubes sit side-by-side.^{[4]
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Use a rag to create a seal around the tubes. This method works by increasing air pressure in the tank to displace the gas through the longer length of tubing and into your receptacle. To create this high air pressure, it's important that no air be allowed to escape the tank. Grab a cheap rag or towel (one you won't mind getting dirty) and pack it around your tubes to create a tight seal. The rag should conform tightly around your tubes but shouldn't compress them and prevent the flow of air and gas.^{[5]
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- If you're having trouble creating a tight seal, try soaking your rag in water and ringing it out, then packing it around your tubes. Wet rags generally create a tighter seal than dry ones.
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When ready, force air into the short tube. Ensure that the end of the longer length of tubing sits comfortably in your gas receptacle, then blow air into the shorter tube to increase the air pressure inside the tank. You may blow with your lungs (in which case, take care not to breathe in through the tube and inhale any fumes), but you may find greater success using a mechanical air pump. Forcing air through the short tube increases the pressure of the air above the gas in the tank, causing it to flow through the longer tube and into the gas can.^{[6]
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- If you're having difficulty, make sure you have a tight seal around your tubes. It's essential to ensure that air can neither enter nor leave the gas tank except through the short length of tubing.
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Monitor the flow of gas. As you blow into the gas tank, you should see gas move through the longer length of tubing and into your gas can (assuming you used clear tubing). Once gas is freely flowing from the tank into the can, you don't need to continue blowing - gravity will do the rest of the work. When you want to stop siphoning gas, cover the long tube with your thumb, raise it above the level of gas in the tank, and remove your thumb. Any remaining gas in the tube should flow back into the tank. Congratulations! You're finished. Remove your tubes and close the gas tank.^{[7]
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- If the gas in the tube won't flow back into the tank when you want to stop siphoning, ensure that the short tube is free of obstruction and, if necessary, remove the seal around the tubes. Air needs to be able to escape the tank to make space for the gas flowing back in.
Avoid gasoline in your mouth with new siphoning methods. "I always siphoned gas by mouth before, but I hated how the gasoline tasted so bad. After reading this, I tried using the tubing and pressure tricks. Now, I can get gas out of my lawnmower without getting any in my mouth. The instructions on making a tight seal and dealing with air bubbles were super clear and helpful. No more gross mouthfuls of gas for me!" - Bill C.

Retrieve every last drop of fuel. "I was driving my old car when it suddenly ran out of gas miles from the nearest gas station. Luckily I had some tubing in my trunk. I followed the steps here to siphon the last drops of gas from my tank into a gas can. I was able to get every last bit out. The little gas I siphoned let me drive to the station to fill up. If it wasn't for these instructions, I would've been stranded!" - Gerald C.

Control gasoline flow with valves. "I built a siphoning system using the tips here. I attached check valves at each end and a shut off valve in the middle. Now I can stop the flow before air gets in the line. The valves let me easily control how fast the gasoline flows. I can even store gas in it long term without having to re-prime it. This makes siphoning gas a total breeze." - Michael Taylor

Get free gas from a broken-down car. "My working car was empty, and I didn't have money to fill it up. Luckily, I had an old, broken-down car in my driveway with some gas still in it. Using the steps here, I siphoned gas out of my old car and into my working one. It wasn't exactly honest, but it let me drive to work to earn money for more gas. This guide made siphoning gas seem quick and harmless. Now I know how to get free gas in a pinch." - Keaton G.

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Method 2

Method 2 of 3:

Using a Siphon Pump

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1
Buy or obtain a siphon pump. If you'd prefer not to work with an improvised siphon, specialized siphon pumps are commercially available for as little as $10-$15. These pumps come in a wide variety of shapes and sizes - some are automatic, while others are hand-powered. However, the vast majority function similarly: a pump in the middle of a length of tubing creates suction which pulls liquid from one end of the tubing to the other.^{[8]
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- These pumps allow you to safely and easily siphon gas without getting your hands dirty or risking exposure to gas fumes. As such, they're ideal choices for cautious-minded individuals.
2
Place a gas can on the ground beneath the tank and run the tubing from the tank to the can. Like the other methods described in this article, suction only provides the initial force necessary to start the siphon. After gas begins flowing, gravity does the rest of the work. Because of this, it's crucial for the receptacles to be below the level of gas in the tank.
- Note: siphon pumps have one designated end that liquid enters and another end from which liquid leaves. Ensure that the correct ends of the tubing are being used. If arranged backwards, the pump will simply push air into the gas tank.^{[9]
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Pump when ready. Because siphon pumps work in a wide variety of ways, the exact action you'll need to take here may vary. If you have a hand-operated pump, you may need to grab a plunger and push in and out or squeeze an inflatable bulb. If you have a mechanical pump, you may just need to flip a switch.^{[10]
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- Most hand-operated pumps only require a few pumps to get liquid flowing - after this, gas should flow freely.
- Automatic pumps may or may not need to be left on throughout the pumping process. Consult any instructions provided with your siphon pump for more information.
Raising the end of the tubing to a level higher than that of the gas in the tank cause the flow of gas to reverse, so any residual gas in the pump should drain back into the tank. If using an automatic pump, you may need to turn it off at this point.
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Remove the siphon pump from the tank. When the tubing is free of excess gas, you may safely remove it from the gas tank. You are finished. Close the gas tank and seal the gas can, then safely disassemble and store your siphon pump.
- Some siphon pumps need to be cleaned after use. Consult any provided instructions for more information - often, all that's necessary is to pump a mixture of soap and water through the device and let it air dry.

Method 3

Method 3 of 3:

Traditional Mouth Siphoning (Not Advised)

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1
Understand the danger of gasoline poisoning. Gasoline contains numerous chemical compounds called hydrocarbons which are poisonous to humans.^{[11]
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Research source} Swallowing gasoline or breathing in its vapors can lead to numerous unpleasant (even potentially life-threatening) symptoms, including difficulty breathing, localized irritation, vision loss, stomach pain, vomiting (sometimes with blood), drowsiness, cognitive impairment, and many more. If attempting this method of siphoning, take every possible precaution to ensure you don't swallow any gasoline or breathe in any vapors.
- If you've been exposed to gasoline in any way and begin to exhibit symptoms, call the emergency services or your local poison control central immediately.
As with the method above, this method requires a length of tubing and a receptacle to contain the siphoned gas. As above, it's important to use a closed gas canister to prevent gas from being spilled or fumes from being inhaled. However, with this particular method, clear tubing is not merely recommended, but rather, crucial. Because ingesting gas is hazardous to your health, you need to be able to able to see the gas moving through the tube so that you can take the tube out of your mouth before gas reaches it.
Set your gas can on the ground near the vehicle's gas tank. Feed one end of the tube into the tank deep enough that it sits below the surface of the gas into the tank. To tell whether the tube sits below the gas, blow air into the other end (taking care not to inhale fumes through the tube as you do so) and listen for the sound of bubbles.^{[12]
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This method of gas siphoning works by using your mouth to create suction in the tube, which draws gas out of the tank. Once gas is flowing freely, gravity causes the siphon to continue sucking gas out of the tank. Care must be taken to ensure you don't swallow any gas or inhale any vapors. Once the tube is in your mouth, breathe only through your nose and pay close attention to the level of gas in the tube.
Once you start sucking on the tube, gas may begin flowing quickly. Keep one hand ready to stop the flow of gas so that none gets in your mouth.
To minimize (but by no means eliminate) the risk of gas vapor inhalation, try to suck with your mouth, rather than your lungs - as if you are drawing on a cigar, rather than a cigarette. When gas begins flowing through the tube, it can flow somewhat quickly, so be alert. When the gas is about six inches from your mouth, crimp the tubing tightly near the end and remove it from your mouth.
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Check for air bubbles in the tubing. Air bubbles are a common hindrance when siphoning gas, as they can impede proper flow, forcing you to suck harder, which is dangerous. If you see air bubbles in the tubing, release the crimp and drain the gas back into the car, then try again.
- Try to position the tube so that you're sucking directly above the tank. According to some sources, air bubbles are more common when the tube runs to the side, rather than up and down.
The gas should begin to flow into the gas can. From this point on, the power of gravity should continue pulling gasoline from the tank and into the can. Monitor the flow of gas to ensure that the can is filling at a steady pace.
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Pull the tubing up out of the tank when you have nearly reached the desired amount of gas. Doing this stops the flow of gas and allows the gas remaining in the tube to drain safely into your gas can. Account for the volume of gas remaining in the tube before pulling the tube out of the tank - you don't want to wait too long and risk an overflow.
- Alternatively, simply cover the free end of the tubing and lift it higher than the level of gas in the tank. Gravity will cause the gas to flow back into the tank. You can even lift the gas can itself while the tube is still in it for the same effect.
You've finished! Close your gas tank and seal your gas can to prevent the inhalation of fumes.

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Question

Can I siphon straight from one car to another?

Community Answer

Yes, as long as the gas level in the car you are siphoning from is higher than the end of the hose where gas comes out.

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If my car is on a hill, can I still siphon gas?

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Yes, when siphoning, you create a vacuum, thus letting the flow of gas overpower the force of gravity.

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Is this method cheaper than buying gas?

Community Answer

Siphoning gas from another vehicle is free, but it's illegal. If you get caught, you will have to pay a fine and/or court costs, in which case it will not be cheaper and it will certainly be more inconvenient.

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Warnings

The fumes from it can be bad for your lungs and can taste really bad. If you want, use a siphon pump.

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Be careful that the gas can doesn't overflow.

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Be careful not to get any gas in your mouth. Only use tubing where the gasoline level can be seen. Inhaling or swallowing gasoline can have serious harmful effects. May be toxic if it contains tetraethyl lead.

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Don't smoke or allow flames or sparks nearby.

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