Drain Gas From Your Lawn Mower: Different Methods

If you’re looking for multiple different methods to drain gas from your lawn mower, look no further!

Perhaps this is something you never considered.  Maybe you didn’t know that there are instances where you need to drain the gas out of your lawn mower.  Or perhaps you know that it needs to be done, but you don’t know how to drain gas from lawn mower engines.

If you fit this description, then you definitely need to read this whole article.

We will discuss why you need to drain gasoline out of your lawn mower’s fuel tank.  You will also learn when the mower’s gas tank should be drained.

To wrap it all up, we will detail the different methods you can use to drain the gasoline from the engines of different kinds of lawn mowers.

So, whether you are doing this for the very first time or simply need a refresher course to hone your skills, everything you find here will help to ensure that you know what to do when the time comes to drain the gasoline from your lawn mower’s engine.

Why Does the Gas Need to Be Drained?

You have spent the last few months diligently mowing your lawn.  But now the weather is beginning to turn cold and your lawn has gone dormant.  The grass is no longer growing and the mowing season has come to a close.

A common mistake that people make is to put the machine in the garage and leave the remaining gas in the engine.  Then, when it’s time to take out the lawn equipment in the spring, they have trouble making the engine run correctly.

It sputters.  It hesitates.  Sometimes the machine won’t fire up at all.

They scratch their heads and wonder, “What’s the problem?”

One of the primary problems is the old gas that sat in storage for months.

Gasoline is a combustible liquid that relies on volatile compounds to burn.  Over time these volatile compounds evaporate.  This makes the old gasoline less combustible.  That is no good.

As the compounds evaporate, they create gummy like deposits throughout the entire fuel system of the engine. 

The gas deposits will sink to the bottom of the fuel tank and reduce the quality of the gasoline.  When you start the engine and run old gasoline through the motor, it will clog up the fuel line, fuel filter, and carburetor.  This can render your lawn mower inoperable.

Instead of making that mistake, keep your lawn mower in working condition by draining the gas before you put it away for the winter.  In truth, gasoline can go stale in as little as 30 days.

So if you’re going out of town for business or will be indisposed for an extended period of time, it would behoove you to drain the gas tank of your lawn mower.

Draining the gas tank is a critical step in the winterization of your lawn mower and other pieces of equipment like trimmers and leaf blowers. Just like your lawn needs to be winterized, so too does your lawn equipment.

How Do You Siphon the Gas From a Lawn Mower Engine?

Siphoning is a tried and true method for draining a gas tank.  This method is used for lawn mowers that don’t have fuel lines that are easy to reach and disconnect.

While siphoning drains fuel from the tank effectively, it will leave gasoline in the fuel line, fuel filter, and carburetor.

Using a siphon can be a go-to technique if, by chance, you find yourself in an emergency.  Whether it be a vehicle or a lawn mower, this method is useful for any tank you might encounter.

Here are the steps to take if you choose to use a siphon to drain a gas tank.

Step 1:  Prepare the Engine

A fuel stabilizer is a treatment that extends the life of the gasoline in the engine.  The additives in the stabilizer prevent the gas from breaking down into gummy deposits and keeps the fuel fresh for longer periods of time.

So before you drain the gasoline from the engine, add a fuel stabilizer and allow the motor to run for a few minutes.  This will circulate the stabilizer through the fuel line, the fuel filter, the tank, and the carburetor.

The treated gasoline that is left behind in these parts of the fuel system will remain combustible and can be stored safely through the winter. 

Do not store untreated gasoline for extended periods of time.

Step 2:  Cool Down on a Flat Surface

Once you have circulated the fuel through the engine, allow it to cool down before you begin working on it. 

Whether you have a push mower or a riding mower, you need to ensure you are operating on a flat surface. 

If the lawn mower is not on even surface, oil from the oil reservoir will run out and cover other parts of the motor.  So a flat, even surface is key.

Riding mowers should engage the emergency brake to ensure they remain stationary.

Because gravity is the force behind the siphon technique, the container that the gas will be siphoned into must be lower in elevation than the tank. 

If you have a push mower, be prepared for some heavy lifting.  An easy way to ensure that the lawn mower is resting on a flat surface is to place the deck of the mower onto two saw horses.  Space the saw horses close enough to fit within the wheelbase of the mower.

Step 3:  Pull the Plug

To avoid potential hazards and danger, disconnect the spark plug wire and remove the spark plug.  With the spark plug removed from the engine, you can be sure that it won’t start up accidentally. 

You do not want a spark plug to accidentally start a spark with gas flowing outside of the tank.  One spark can ignite the flammable gasoline and result in a deadly explosion.

Step 4:  Choose Your Method

Step 4 comes with options.  There are three methods you can use to siphon gasoline out of a tank.  All three methods involve a clear hose, a container placed below the tank, and gravity.  Here is a quick look at each different method:

Method 1:  Increasing the Internal Air Pressure

You will need a clear hose cut into two different lengths: one short and one long.

The longer hose will be run from the container on the ground into the gas tank.  This hose should rest on the bottom of the tank to ensure that it is submerged in the fuel.

The shorter hose will also be inserted into the tank.  However, it will remain above the fuel level line in the tank.

Use an old, wet shop rag to seal the gas cap around the two hoses so that air cannot escape the tank. 

Once the cap is sealed, blow air into the tank through the shorter tube.  Blowing into the tube, either with your mouth or with an air compressor, increases the air pressure within the tank.  This will cause the gas to flow through the longer tube and down into your container.

Once gas begins to flow freely, you no longer need to blow air into the shorter piece of hose.  By this point, gravity has taken over and will finish the job on its own.

Method 2:  Siphon Pump

The safest, fastest, and most convenient way to siphon gasoline is to use a siphon pump. 

Some pumps are automatic and only require you to flip a switch, while others are manually operated by hand.

No matter which style of siphon pump you use, they all function in basically the same manner.

Siphon pumps consist of clear tubing with a pump in the middle.  The pump provides the initial suction required for the gas to begin flowing.

Once the gas is steadily flowing through the tubing, gravity will take over and finish the rest.

The tubing on a siphon pump has two different ends that serve distinct purposes.  So don’t make the mistake of putting the hose in backward.  The side of the hose that goes into the tank is generally the brass end.

Insert the brass end into the tank and submerge it in the gasoline.  Squeeze the pump a few times, begin the required suction, and then watch gravity take over.

Method 3:  The Last Resort

Honestly, in the grand scheme of things, you probably won’t need to use this method to siphon gas out of your lawn mower.  Siphoning this way is generally reserved for emergencies and criminal activities.  It’s a means to an end if you have exhausted all of your other options.

Clear tubing is non-negotiable when siphoning gas with this method as you are basically turning the hose into a straw.  Ethanol is not the kind of alcohol you want to drink.

Take one long piece of clear tubing and insert it into the gas tank.  Make sure that end of the hose is submerged in the fuel.

The free end of the hose is not yet inserted into the gas can.  It goes in your mouth instead.

You will use your mouth to create the suction required for the gas to begin flowing through the tube. 

Keep a close eye on the tube so you can see the gas when it begins to flow.  It’s also a good idea to have your hand wrapped around the tube, ready to pinch it off quickly to impede the flow of gasoline.

By that point, gravity will have taken the wheel and will finish the job.  So quickly remove the hose from your mouth and place it in the container on the ground.

Step 5:  Since You’re Already Down There

Once you have removed the tubes and cleaned up any gasoline that might have spilled, you need to do some preventative maintenance on your lawn mower.

Check the air filter to ensure it isn’t clogged with debris.  If it’s dirty and matted with debris, then it’s time to change the air filter.  Air filters are a crucial component in keeping your engine running smoothly.

You need to make sure the oil level in the reservoir is full of clean oil.  Unscrew the oil filter and ensure the adapter is clean of dirt and debris.  If you’ve noticed a drop in your lawn mower’s performance, it’s probably time to change the oil filter.

Step 6:  The Final Clean Up

If possible, put a little bit of fresh gas into the tank and slosh it around to dislodge any remaining residual debris from the old gasoline.  Then drain the new gas out of the engine just as you did with the old gas.

Allow the engine to dry for a few minutes.  No matter how well you think you siphoned the gas, there is always some residual fuel remaining in the tank.  The best way to dry the leftover gasoline is to use an air compressor to blow-dry the tank’s interior.

Once you’ve removed all of the fuel, you can replace the spark plug and the spark plug wire.

Set your walk-behind mower back on the ground. Done.

Now you know how to drain gas from lawn mower engines using a siphon.

Draining Gas From A Lawn Mower Without A Siphon

So you want to know how to drain gas from lawn mower engines without having to use a siphon?  There are a few different ways to do that.

Start Your Engines

The one that requires the least effort but takes the longest is simply allowing the engine to run itself out of gasoline.  Just make sure you add the fuel stabilizer before you crank it up.  That way, any fuel left in the engine will have been treated and won’t break down over the winter months.

The Lucky Few With Fuel Lines Connected Directly to Carburetors

A fortunate few of you out there have mowers that have a fuel line connected directly to the carburetor that is easy to reach.

If you have a lawn mower like this, grab a container for the fuel and disconnect the fuel line from the carburetor.  This will allow the fuel to flow from the tank through the line and into the receptacle.

Once the gas is completely drained, attach the fuel line back to the carburetor. 

Don’t forget to check the air and oil filters along with the oil level once you’ve finished. 

Turkey Baster Method

Imagine this worst-case scenario: You can’t run the motor at all because the gas has gone bad, you don’t have a siphon pump or a length of clear tubing, and you can’t get to the fuel line to drain the tank.

What can you do?

It may sound silly, but you need to venture into the kitchen and grab a turkey baster. 

Yes, a turkey baster.

Put the baster into the tank and squeeze the baster’s bulb for suction.  Take the gas from each full baster and put it into a proper gas receptacle.

This may take a little time and feel a bit odd, but it is an effective tool for draining gasoline.

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Happy Planting!

About the author: Carley Miller is a horticultural expert at TheGreenPinky. She previously owned a landscaping business for 25 years and worked at a local garden center for 10 years.

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