How To Drain Gas From A Lawn Mower

Before you store your mower for the season, removing the old fuel is a crucial maintenance step. Learning how to drain gas from a lawn mower properly can prevent costly repairs and ensure a quick start next spring. Gasoline left in the tank and carburetor can degrade, forming gummy residues that clog the engine’s delicate fuel system.

This guide provides clear, step-by-step instructions for this essential task. We’ll cover the tools you need, safety precautions, and several effective methods to get the job done right.

Draining the gas from your lawn mower is a straightforward process, but it requires careful preparation. The method you choose often depends on your mower’s design and your personal preference. The primary goal is to remove all liquid fuel from the tank, fuel lines, and carburetor bowl.

Having the right tools and a plan makes the task much easier and safer. Always work in a well-ventilated area, away from any open flames or sparks, including your water heater or furnace pilot light.

Essential Tools And Safety Gear

Gathering your supplies before you start is key to a smooth process. You likely have most of these items already in your garage or workshop.

A pair of safety glasses to protect your eyes from fuel splashes.
Chemical-resistant gloves, such as nitrile gloves.
A set of basic hand tools, including screwdrivers and an adjustable wrench.
A siphon pump or a hand-operated fluid transfer pump.
A clean, approved fuel container for collecting the old gasoline.
A flat pan or tray to catch any drips or spills.
Some clean rags or paper towels for cleanup.
A fuel stabilizer for treating any fresh gas you plan to leave in the tank (optional).

Pre-Draining Safety Checklist

Safety must be your top priority when handling gasoline. Follow this checklist to minimize any risks.

Allow the engine to cool completely if you have just used the mower. A hot engine is a fire hazard.
Disconnect the spark plug wire. This prevents the engine from accidentally starting while you are working on it. Secure the wire away from the spark plug terminal.
Position the mower on a flat, level surface in your driveway or garage with the door open.
Have a fire extinguisher rated for flammable liquids readily accessible, just in case.

Choosing The Right Fuel Container

Never drain gasoline into a milk jug, glass jar, or any container not designed for fuel. Use only a red plastic gasoline can that is UL-approved or metal safety can. These containers are designed to safely vent pressure and prevent explosions.

Method One: Using A Siphon Pump

This is often the cleanest and easiest method, especially for mowers with a fuel tank that is difficult to access or tip. A simple hand pump siphon is inexpensive and very effective.

Place your empty fuel container on the ground, lower than the mower’s gas tank.
Insert the siphon pump’s longer tube into the mower’s fuel tank.
Place the shorter tube or pump outlet into your empty fuel container.
Follow the pump’s instructions to start the siphon. This usually involves squeezing a primer bulb or pumping a handle a few times.
Once the flow begins, the gasoline will transfer into your container until the tank is empty. You may need to tilt the mower slightly to get the last bit of fuel from the corner of the tank.

Method Two: Draining Via The Fuel Line

If your mower has a fuel line running from the tank to the carburetor, you can often drain the tank by disconnecting this line. This method also helps clear the line itself.

Locate the fuel line. It is a small rubber or plastic hose connecting the bottom of the gas tank to the carburetor.
Place your drain pan directly underneath the connection point at the carburetor or the fuel tank outlet.
Using pliers if necessary, loosen the hose clamp and carefully pull the fuel line off the carburetor nipple.
Allow the gasoline to flow freely from the tank into your drain pan. You can direct the hose into your fuel container once the initial flow slows.
Once drained, reconnect the fuel line and secure the clamp. Check for any leaks by turning the fuel valve on, if your mower has one.

Method Three: Removing The Gas Tank

For some mower models, particularly older ones or those with a very simple design, it may be easiest to remove the entire gas tank. Consult your owner’s manual first to see if this is recommended.

Use your siphon or the fuel line method to remove as much gas as possible first.
Disconnect the fuel line from the tank if you haven’t already.
Remove any screws or bolts holding the tank in place. Be careful, as there may be a small amount of fuel left.
Lift the tank out and pour the remaining fuel into your container. This is a good opportunity to inspect the tank for rust or debris.
Reinstall the tank securely and reconnect the fuel line when finished.

Draining The Carburetor Bowl

Even after draining the main tank, a significant amount of old fuel remains in the carburetor’s float bowl. Draining this is critical for complete winterization.

Locate the carburetor. It is usually a small metal or plastic box attached to the side of the engine, connected to the air filter and fuel line.
Find the drain screw or bolt at the very bottom of the carburetor bowl. It may be a flat-head or hex-head screw.
Place your drain pan directly beneath this screw.
Slowly loosen the drain screw with the appropriate screwdriver or wrench. Fuel will begin to drip out.
Allow all the fuel to drain completely, then tighten the screw back snugly. Do not overtighten, as you could strip the threads.

What To Do With The Old Gasoline

You should never pour old gasoline down a drain, onto the ground, or into the regular trash. It is hazardous waste and must be disposed of properly.

Check with your local government or waste management authority for household hazardous waste (HHW) collection days or permanent drop-off facilities.
Some auto parts stores or service stations may also accept old gasoline for a fee.
If the gasoline is relatively fresh (less than a month old) and uncontaminated, you can mix it with a large amount of fresh gas in your car’s tank. Use a ratio of no more than one part old gas to ten parts new gas.

Final Steps After Draining

Once the fuel system is empty, there are a few final steps to prepare your mower for storage.

Consider running the engine until it stalls. After reconnecting the spark plug wire, start the mower. This will burn off any tiny residual fuel in the carburetor jets. Let it run until it stops on its own.
Reinstall the spark plug wire to its proper position or, for long-term storage, you may choose to leave it disconnected.
Wipe down the entire mower, especially around the fuel cap and carburetor, to remove any gas residue.
Store your mower in a cool, dry place, preferably with the fuel cap loosened slightly to prevent pressure build-up from temperature changes.

Preventative Tips For Fuel System Health

Taking proactive steps can reduce the need to drain gas as often and extend the life of your mower’s engine. Good fuel management is the best maintenance you can perform.

Using Fuel Stabilizer

A fuel stabilizer is an additive that prevents gasoline from breaking down for up to 24 months. This is the best alternative to draining if you plan to store your mower for a shorter period or want to keep the tank full to prevent condensation.

Add the stabilizer to a fresh tank of gasoline *before* filling your mower, or add it directly to the mower’s tank and then run the engine for 5 minutes to circulate it through the carburetor.
This treated fuel can be left in the tank over the winter, ready for spring.
Always follow the stabilizer product’s instructions for the correct ratio.

Buying The Right Gasoline

The type of gas you use makes a big difference. Modern ethanol-blended fuels (E10) attract moisture from the air, which leads to phase separation and corrosion inside your fuel system.

Whenever possible, use ethanol-free gasoline (often called “recreational fuel”) in your small engines. It is more stable and less likely to cause issues.
If you must use E10 gas, try to buy it in smaller quantities and use it within 30 days.
Never use gasoline with more than 10% ethanol (E15, E85) in a lawn mower, as it can cause severe engine damage.

Frequently Asked Questions

How Often Should I Drain The Gas From My Lawn Mower?

You should drain the gas if you plan to store the mower for more than 30 days without using a fuel stabilizer. For seasonal storage over winter, draining is highly recommended. If you use a stabilizer in fresh gas, you may not need to drain it each season.

Can I Leave Gas In My Lawn Mower Over Winter?

It is not advisable to leave untreated gasoline in your mower over winter. The fuel will degrade and likely cause starting problems or carburetor clogs in the spring. If you leave gas in, it must be treated with a high-quality fuel stabilizer.

What Is The Easiest Way To Get Gas Out Of A Lawn Mower?

For most people, using a simple hand-operated siphon pump is the easiest and cleanest method. It requires minimal disassembly and allows you to transfer the fuel directly into a storage container without spills.

Why Won’T My Lawn Mower Start After Sitting With Old Gas?

Old gas forms varnish and gum that clogs the small jets and passages inside the carburetor. This prevents the proper fuel-air mixture from reaching the engine. Draining the old gas and cleaning the carburetor is usually required to fix this common problem.

Do You Have To Drain The Carburetor On A Lawn Mower?

Yes, for complete fuel removal, draining the carburetor float bowl is essential. A significant amount of fuel sits there, and it will evaporate and leave behind sticky residues if not drained. The small drain screw on the bottom of the carburetor makes this a simple task.