What Happens if Water Gets in Your Gas Tank?


Most people know that you should only put gas in your gas tank, but not everyone knows the exact consequences of putting other items, such water, in a gas tank. You may tell when this happens accidentally when it causes certain symptoms and issues. What occurs if water is introduced to a gas tank?

Your engine’s parts will deteriorate if water gets into your gas tank. This includes the gasoline tank, fuel pump, fuel filter, fuel injector, and ultimately the entire engine. Metal parts will rust, electronic parts like fuel injectors will be destroyed, and the engine won’t operate in the presence of water.

What happens if water gets into your gas tank? How can you tell if water is in your gas tank? What should you do if water gets into your gas tank? All of these topics are covered in this article.

Problems with Water in Gas Tank

For a variety of reasons, water can enter your gas tank, and you might not always notice it right away.

For instance, you might have unintentionally left your gas cap off before it started to rain, a car might have been left outside for some time, or a sketchy gas station might have filled your tank with gas and water. The issue arises once the water enters your gas tank, regardless of how it got there.

What Engines Do

You must first grasp how engines function to comprehend why water is terrible for engines.

An engine has to pump fuel from the gas tank to the engine, where it burns, in order to run. This combustion physically moves the crankshaft through the pistons of the engine.

Though there is more to it, as this page from the Department of Energy demonstrates, the crucial fact that gasoline is used to power the engine must be understood.

Small amounts of water are typical in fuel tanks, and even gas contains a very small quantity of water, but on average, water makes up much less than 1% of gas. Condensation can be brought on by empty gas tanks and tiny condensation drips that can be seen on fuel caps. This condensation is particularly prone to occur in places with high humidity or rapid temperature changes.

You will experience issues, though, if your gas tank has an excessive amount of water.

What Happens if A Gas Tank Has Too Much Water?

Water doesn’t burn as fuel does, so it can’t power an engine like gas or other fuel, so having too much water in a gas tank is a simple problem.

Engines splutter or otherwise become unresponsive if too much water is in the gas tank. Water can damage the engine and fuel injectors if you overlook the problem and allow it to enter.

Water in your fuel system is bad because it corrodes metal and damages delicate electronics, including those in your injectors. The engine stops working when fuel injectors are unable to calculate how much fuel to feed into the engine to make it run.

Additionally, the sensors misread the fuel due to water in the fuel. It might interpret the fuel mixture incorrectly as either too rich, which indicates there is too much gasoline, or too lean, which means too much air.

Why Does Water Residue in The Gas Tank?

When water collects in the gas tank, it can cause rusting and, if an electric fuel pump is totally immersed, it can be destroyed by a significant amount of water. Your gasoline filter, which is designed specifically to handle fuel, can also become clogged by it.

Sputtering, abrupt performance changes (from sputtering to screaming engines), and generally poor performance are most frequently caused by sensors misreading the fuel-air combination entering your engine.

Again, if water is allowed to remain for too long, misreading the gasoline will progress to outright failure of the fuel injectors.

You need to take action immediately if you think your gas tank may have considerable water in it. If you choose to ignore it, the cost of repairs will continue to rise.

The Symptoms of Water in A Gas Tank

Water in your gas tank will cause specific symptoms, and the severity of these symptoms depends heavily on how much water there is. The general signs remain the same, however.

Some symptoms to keep your eye out for include:

  • Sputtering when you try to start the engine, especially immediately after filling up.
  • The engine stalls completely, especially right after refueling the tank.
  • Jolting as the engine alternately tries to combust fuel, then water, or vice versa.
  • White smoke issuing from your exhaust is caused by the engine turning water into steam.
  • The engine refused to start at all. This is because the water interferes with the engine’s needed rich fuel-air mixture.
  • The check engine light turns on, often after refueling or starting the engine for the first time that day.

How Much Water in A Gas Tank Will Ruin a Car?

There’s no definitive answer for how much water in your gas tank is too much. That said, as little as one cup of water in your gas tank can cause serious problems, and any more than that will definitely be noticeable. If over a cup of water gets into the gas tank, your car will probably not work.

The good news is that in most cases, water in your gas tank won’t immediately ruin the engine. The bigger problem is ignoring the issue rather than the water itself because letting it sit in your engine and corroding its components is the main way it causes damage.

How to Check for Water in Your Gas Tank

To tell if water is in your fuel tank, check for the presence of the above-listed symptoms. Follow these steps to see if water is in your tank:

  • Find the low point of your fuel tank and drain it.
  • You need the low point because water is denser than gas and sinks quickly after it gets into the tank.
  • Open the drain and collect the fluid that comes out.
  • You’ll be able to instantly tell the difference between water and gas as the water will settle to the bottom, as gas and water don’t mix.
  • If you find water in your gas tank, you’ll need to take some additional steps to completely rid it of water. If you don’t and the water stays there, it can and will quickly degrade and destroy your engine.

How to Remove Water in Your Gas Tank

There are a few ways to remove water from your gas tank, depending on how much is in there.

If it’s only a small amount of water, there are certain additives you can pour into the gas tank to get the water out. If there’s a lot of water in the tank, the whole tank should be drained to be certain it gets out.

Let’s look at the two methods you can use to remove water from your gas tank.

#1 Additive Method

Some people think that rubbing alcohol is a suitable additive to remove water from gas tanks, but you should absolutely not use it. Rubbing alcohol has water in it already and has no way to actually get the water out of the gas tank.

Instead, I recommend using a water remover product like ISO-HEET Water Remover from Amazon. This product is five times more absorbent than regular gas dryers.

Of course, you don’t have to use this product in particular, but you should only use a reputable water remover product, not a home remedy. These products are often advertised as a fuel line or fuel injector cleaners.

To remove water with water remover, you will need to:

  • Add the entire bottle to the gas tank before or after refueling the tank.
  • Drive as usual.

For small amounts of water, ISO-HEET or similar products will remove water from your fuel tank and lines before it can cause any problematic damage. However, for larger amounts of water, it won’t do much good.

#2 Drainage Method

Draining a gas tank is the best and most surefire way of removing water before it can corrode and damage the engine. It may be difficult sometimes, but it’s always worth doing. Would you rather drain the tank or rebuild the engine?

Some people opt to try siphoning the tank, but this is a challenging task that poses a fire hazard and isn’t guaranteed to work, which is why I don’t advise trying it.

The exact steps for this method depend on whether your gas tank has a drain or not. If so, the step is as simple as opening the drain and collecting what comes out.

If not, the process gets more complicated.

To drain a fuel tank without a drain, you will have to:

  • Remove the fuel tank. The exact steps vary based on your vehicle’s make and model.
  • Drain the fuel tank manually.
  • Replace the fuel filter. While it may have been damaged, it’s better to be safe than sorry.
  • Pour fuel cleaner into the gas tank with fresh gas.
  • Run the engine for 30 minutes to flush the fuel lines.

Final Thoughts

Water in a gas tank can be a major issue and cause significant amounts of damage. However, there are obvious signs that signal its presence. If you think you have water in your gas tank, use a fuel additive or fully drain the tank to get it out, depending on how much water is in there.