How To Empty Gas From A Lawn Mower
If your mower is hard to start, you’re getting ready for winter storage, or you’ve accidentally filled up with the wrong fuel, emptying the gas the right way will save headaches later. I’ve drained dozens of tanks over the years—walk-behind mowers, riders, and everything in between—and the process is straightforward if you take a few precautions. Here’s exactly how I do it, plus some tips that come from hard-earned, grass-stained experience.
Why You Should Empty The Gas
Old gasoline turns to varnish, gums up carburetors, and clogs tiny jets that are fussy on small engines. Ethanol blends attract moisture, which leads to rust inside tanks and white deposits in carb passages. If the mower sits more than about a month without stabilizer, I plan to drain it. I also empty the tank any time the fuel looks cloudy, smells sour, or if I need to service the carburetor, fuel line, or filter.
Safety First
- Work outside or in a very well-ventilated area away from flames, heaters, or sparks.
- Let the engine cool completely.
- Disconnect the spark plug wire on walk-behind mowers. On riders, remove the key and disconnect the negative battery cable.
- Wear gloves and safety glasses. Keep rags and a fire extinguisher nearby.
- Use an approved gasoline container and a fuel-safe siphon or hose.
“Gasoline is flammable and sneaky—it loves to find the one pilot light you forgot about. Give it respect and take your time.”
What You’ll Need
- Approved gas can or drain pan
- Hand siphon pump or clear fuel-safe hose
- Pliers for spring clamps on fuel lines
- Fuel line clamp or locking pliers with a rag to protect the hose
- Flathead screwdriver or small wrench (for carburetor bowl drains)
- Shop rags and paper towels
- Carb cleaner (optional, for a quick rinse)
Three Reliable Ways To Empty The Tank
The Siphon Method
This is my go-to when the tank is accessible and I don’t want to crack any lines.
- Place your gas can lower than the mower’s tank so gravity helps you.
- Insert the siphon hose into the tank until it reaches the lowest point.
- Use the siphon pump to start flow. If you’re using a simple hose, fill it with fuel first or use a primer bulb—never mouth-siphon gasoline.
- Drain until the flow stops. Tip the mower slightly if needed to reach the last bit, keeping the air filter side up to prevent oil from running into the filter.
Pro tip: On most walk-behind mowers, tilt the mower so the air filter and carburetor are on the high side. That prevents oil from migrating into the intake. Always check your engine manual if you’re unsure.
The Fuel Line Method
Helpful when the tank opening is awkward or you want to drain both the tank and the line.
- Find the fuel line that runs from the tank to the carburetor. It’s usually a black rubber hose.
- Clamp the hose near the tank to stop flow.
- Place a container under the carb area. Use pliers to slide the spring clamp back, then gently pull the hose off the carb inlet.
- Aim the hose into your container and remove the clamp. Fuel will flow out quickly. Control the hose so it doesn’t whip around.
- When the tank is empty, reattach the hose to the carb and secure the clamp.
This method is fast and works great on riders and walk-behinds. While you’re there, check the fuel line for cracks and replace if it’s stiff or glossy from age.
The Carburetor Bowl Drain Or Removal
Some carburetors have a drain screw or a hex bolt on the bottom of the bowl. This empties the last bit of fuel that sits in the carb and causes starting issues.
- Put a rag or small cup under the carb bowl.
- If there’s a drain screw, loosen it and let the fuel trickle out. If not, remove the center bolt to drop the bowl—gently, there’s usually a thin gasket.
- Drain, wipe the bowl, and spritz a bit of carb cleaner if you see varnish. Reinstall carefully.
If your carb has no drain and you don’t want to remove the bowl, run the engine after you’ve drained the tank. Let it idle until it stalls to burn off the residual fuel in the carburetor.
Step By Step For Walk-Behind Mowers
- Cool the engine and pull the spark plug wire.
- Open the fuel cap and check for debris or water. If you see layers (water sits at the bottom), plan to fully drain and clean the tank.
- Siphon or disconnect the fuel line to drain the tank.
- Drain the carb bowl or run the engine dry after refilling with a splash of fresh gas if needed.
- Wipe up spills, check the air filter, and reattach the spark plug wire.
Step By Step For Riding Mowers
- Remove the key, set the brake, disconnect the negative battery cable.
- Find the fuel shutoff valve near the tank or filter. Close it. If there isn’t one, clamp the line.
- Place a can under the line, loosen the clamp at the filter or carb, and direct the hose into the can.
- Open the shutoff valve or remove the clamp to drain. Riders often drain faster due to larger lines.
- Don’t forget the fuel filter—replace it if you’re dealing with contaminated fuel.
- Crack the carb bowl drain if equipped, or run the engine briefly on fresh gas and then shut it off to clear the bowl.
How To Handle The Last Little Bit
No matter what you do, there’s usually a teaspoon or two left in nooks and crannies. I either tip the mower slightly (again, keeping the air filter up) or add a small amount of fresh gas with stabilizer, slosh it around, and drain again. That mini rinse dilutes varnish and helps prevent sticky deposits.
What If No Fuel Comes Out
- Check for a closed fuel shutoff valve near the tank.
- Look for a kinked hose or a clogged fuel filter.
- On old hoses, the inner liner can collapse—replace the hose.
- Make sure the gas cap vent isn’t blocked. Crack the cap and try again.
Disposal And Reuse
Old fuel is hazardous. The best option is your local household hazardous waste facility. Many municipalities take gasoline for free on set days. If the fuel is only a little old, looks clear, and doesn’t smell like varnish, you can dilute a small amount into a vehicle with a full tank—think one part old to at least five parts fresh. Always check local rules and never pour gasoline on the ground, down drains, or into soil.
After Draining: Fresh Fuel And Preventive Care
- Use fresh, name-brand gasoline with an ethanol content your manual approves. I prefer ethanol-free when I can get it; small engines run happier.
- Add fuel stabilizer if the gas will sit more than a month. Stabilizer can extend usability up to a year, sometimes longer.
- Label your gas can with the date you filled it.
- Run the mower for a few minutes after refilling to circulate fresh fuel through the carb.
“A few bucks of stabilizer and the habit of labeling your can will save you a spring full of pull-start workouts.”
Common Questions
Can I just run the mower until it dies
Yes, running it dry is better than leaving a full tank of old gas. But it usually doesn’t remove everything in the tank or carb bowl. For long storage, I prefer to drain, then run it dry.
Is a turkey baster okay
Only if it’s fuel-safe. Many kitchen basters soften or melt with gasoline. A small hand siphon is inexpensive and safer.
Should I clean the carb after draining
If the fuel was very stale, yes. At minimum, drain the carb bowl and give it a light spray of carb cleaner. If the mower still surges or won’t start, a more thorough cleaning or a new carb (they’re often inexpensive) might be in order.
How often should I empty gas
Any time the mower will sit more than a month without stabilizer, before winter storage, or if you suspect contamination (water, dirt, wrong fuel). Otherwise, keep fresh, stabilized fuel in the tank and run it every few weeks during the season.
My Personal Routine
At the end of fall, I siphon the tank, open the bowl drain, and add a splash of stabilized fuel. I run the mower for a minute, shut it down, and crack the drain again to leave the carb nearly dry. I tape a note to the handle with the “last run” date. Come spring, it fires on the second pull—no surprise teardowns or sticky jets.
Final Thoughts
Emptying gas from a lawn mower is a simple task that pays dividends. With a few basic tools, safe handling, and the right technique—siphon, fuel line drain, or carb bowl—you can protect your engine, make starts easier, and avoid mid-mow breakdowns. Take it slow, keep the air filter side up when tilting, and treat old fuel like the hazardous stuff it is. Your mower (and your nose) will thank you next season.
