How To Drain Lawn Mower Gas

Learning how to drain lawn mower gas is a key piece of seasonal maintenance that every owner should know. Draining old gasoline from your mower’s tank at season’s end prevents frustrating starting problems next spring. Stale fuel can gum up the carburetor and fuel lines, leading to costly repairs. By taking a little time now, you ensure your mower starts easily when the grass begins to grow again.

This guide will walk you through the entire process, from preparation to safe disposal. We’ll cover the tools you need, several effective methods, and important safety tips. Whether you’re storing your mower for winter or just need to remove bad gas, these steps will help you complete the job correctly.

Before you begin, it’s crucial to gather the right materials and work safely. Gasoline is highly flammable, so always work in a well-ventilated area, away from any open flames or sparks. Let the engine cool completely if you’ve just used the mower. Having everything you need on hand will make the process smoother and safer.

Essential Tools And Safety Supplies

You won’t need many specialized tools for this task. Most items are probably already in your garage or shed. Here’s what to collect before you start:

A pair of safety glasses to protect your eyes from splashes.
Chemical-resistant gloves to keep gasoline off your skin.
A flat pan or a plastic fuel caddy to catch the old gasoline. A baking pan works in a pinch.
A length of clear plastic tubing, about 3/4″ in diameter and 3 feet long.
A set of standard screwdrivers or a socket set, depending on your mower.
A siphon pump, which can be a hand-operated or a simple bulb style.
Several clean, approved fuel containers for storing or transporting the old gas.
Some old rags or paper towels for quick clean-up.

Preparing Your Lawn Mower

Proper preparation sets you up for success. Start by moving your mower to a flat, level surface in your driveway or garage. Engage the parking brake if your model has one. You should also disconnect the spark plug wire to eliminate any chance of the engine accidentally starting. This is a critical safety step that you should never skip.

Next, take a moment to identify the key parts you’ll be working with. Locate the fuel tank, the fuel line (a small hose running from the tank to the engine), and the carburetor. On many mowers, the carburetor is a small metal box near the air filter. Knowing where these are will help you follow the steps more easily.

Checking Your Local Disposal Regulations

Before you drain a single drop, figure out where the old gas will go. Never pour gasoline down a drain, into the soil, or into regular trash. Most communities have hazardous waste collection facilities or specific disposal days. Some auto parts stores also accept old fuel. A quick check with your local waste management authority will give you the correct information for your area.

Method One: Siphoning The Gas From The Tank

Siphoning is often the cleanest and easiest method, especially for mowers without a drain plug. It requires minimal disassembly and is great for nearly full tanks. You’ll need your length of tubing and your collection pan.

Place your collection pan on the ground, lower than the mower’s fuel tank.
Insert one end of the clear tubing deep into the mower’s fuel tank. Try to get it all the way to the bottom.
Put the other end of the tube in your mouth and give a quick, strong suck to start the flow of liquid. Immediately place this end into your collection pan before the gas reaches your mouth. The suction will continue to draw fuel out. Alternatively, use a hand-siphon pump to avoid getting any gas in your mouth.
Allow the tank to empty completely. You may need to tilt the mower slightly to get the last bit of fuel from the tank’s corners.
Once empty, remove the tube and properly seal the gas in an approved container for disposal or recycling.

Method Two: Draining Via The Fuel Line

This method involves disconnecting the fuel line that runs from the tank to the carburetor. It’s very effective and gives you a chance to inspect the hose for cracks or wear. You’ll likely need a pair of pliers or a screwdriver for the hose clamp.

Locate the fuel line where it connects to the carburetor. It’s usually held on by a small spring clamp or a screw clamp.
Place your collection pan directly beneath this connection point.
Using pliers, gently compress and slide back the spring clamp. If it’s a screw clamp, loosen the screw. Carefully pull the fuel line off the carburetor nipple.
Gasoline will begin to flow out immediately. Direct the stream into your pan.
To help the tank drain faster, you can open the gas cap. This releases the vacuum inside the tank.
After the tank is empty, you can reconnect the fuel line or leave it off if you plan to run the engine dry (see next method).

Method Three: Running The Engine Until Empty

This technique is commonly recommended for end-of-season storage. It not only drains the tank but also clears gasoline from the carburetor bowl and fuel lines. This helps prevent deposits from forming inside the carburetor as the fuel evaporates.

Take your mower outside to a well-ventilated area.
Disconnect the spark plug wire for safety, then reconnect it once you’re ready to start the engine.
Start the mower and let it idle. Do not engage the blades.
As it runs, it will consume the fuel in the tank. The engine will eventually sputter and stop when the tank and fuel lines are empty.
Once the engine has stopped, disconnect the spark plug wire again. This ensures the mower cannot start while you are handling it.

Note: Some experts advise against this method for modern mowers with catalytic converters, as running lean can cause damage. Check your owner’s manual for the manufacturer’s specific recommendation.

What To Do With The Carburetor Bowl

Even after draining the tank and line, a small amount of fuel remains in the carburetor’s float bowl. For long-term storage, it’s best to drain this as well. The process varies by mower model, but often involves removing a small bolt or screw from the bottom of the carburetor.

Consult your mower’s manual for the exact location of the drain screw.
Place your pan underneath the carburetor.
Use the correct screwdriver to slowly loosen the drain screw. Fuel will drip out.
Once it stops, retighten the screw snugly, but avoid overtightening which can strip the threads.

Safe Gasoline Disposal And Storage

You now have a container of old gasoline. If the fuel is relatively fresh (less than 30 days old) and uncontaminated, you can reuse it in your car’s gas tank by mixing it with at least a full tank of fresh fuel. This dilutes the old gas and allows your car’s engine to burn it safely. Never use old lawn mower gas in a different small engine.

If the gas is stale, contaminated with dirt or water, or you simply don’t want to reuse it, you must dispose of it properly. As mentioned earlier, contact your local household hazardous waste program. They will provide instructions for drop-off. Always transport gasoline in a sealed, approved container placed in a well-ventilated area of your vehicle, like the trunk or truck bed.

Preventing Future Fuel Problems

The best solution is to avoid having to drain bad gas in the first place. Using a fuel stabilizer is the single most effective step you can take. Add a stabilizer like STA-BIL to every gallon of fresh gas you purchase for your small engines. This treatment keeps the fuel chemically stable for up to 24 months, preventing the varnish and gum that clogs engines.

For seasonal storage, the ideal practice is to either run the engine dry (if recommended) or fill the tank completely with fresh, stabilized fuel. A full tank prevents moisture from condensing inside the tank and causing rust. Simply add the stabilizer to the tank, run the engine for 5 minutes to circulate it through the carburetor, then store the mower.

Common Mistakes To Avoid

Storing the mower with a half-full tank of untreated gas. This invites condensation and fuel degradation.
Using gasoline with more than 10% ethanol (E10) for long periods. Ethanol attracts moisture and can separate from the gasoline. Use ethanol-free fuel if it’s available in your area.
Forgetting to disconnect the spark plug. This is a major safety oversight.
Attempting to drain a hot engine. Always let it cool to prevent burns or fire.
Using makeshift containers like milk jugs for gas storage or disposal. They are not designed for flammable liquids and can degrade quickly.

FAQ: Draining Lawn Mower Gasoline

How Often Should I Drain My Lawn Mower Gas?

You should drain or stabilize the gas whenever you plan to store the mower for more than 30 days. For seasonal storage over winter, it is highly recommended to either drain the system completely or fill it with stabilized fuel.

Can Old Gas Ruin A Lawn Mower?

Yes, absolutely. Old gasoline loses its volatility and forms sticky resins and varnishes. These deposits clog the tiny jets and passages in the carburetor, preventing the engine from getting the correct fuel-air mixture. This leads to hard starting, poor performance, or a complete failure to run.

What Is The Fastest Way To Drain A Lawn Mower Tank?

The fastest method is typically siphoning with a hand pump or disconnecting the fuel line at the carburetor. Running the engine dry takes the most time but has the added benefit of clearing the carburetor bowl.

Is It Better To Drain Gas Or Use A Stabilizer?

Both are effective strategies. For many people, using a fuel stabilizer in a full tank is simpler and just as reliable. For very long storage periods (over a year), draining might be the safer option. Some owners prefer to drain the tank for complete peace of mind.

By following these steps, you can confidently maintain your mower’s fuel system. Properly draining or treating the gasoline will save you time and money, ensuring your lawn mower is ready to go when you need it. Regular maintenance like this extends the life of your equipment and makes yard work much less of a chore.