Water In Gas Tank – Symptomps & Solution

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Stating the obvious here, your car does not appreciate or like water in the engine. Large amounts of water in the fuel system can and will lead to damage and a decrease in engine performance. Learn whether there’s water in the gas tank.

There are various ways water can enter the gas tank. One is through condensation from temperature changes, especially during the winter months when the outside air is cold and the inside of the gas tank is warm. 

adding fuel in gas tank - Water In Gas Tank

Another way is if you forget to secure the gas cap properly, allowing rainwater to enter. However, the most common way is through contaminated fuel at gas stations. This can happen if there is a leak in the underground tanks or if rainwater enters the tanks. This article will cover how to identify if there is water in your gas tank and what steps to take to remove it. 

How Do to Know If There’s Water in Gas Tank 

If you suspect water in your gas tank, a simple way to check is by using a fuel sample bottle (available at auto part stores) and taking a small sample from the tank. If water is present, it will settle to the bottom of the bottle and be visibly noticeable. 

Do not start the car if you see water in the fuel sample. Instead, have a professional drain the gas tank and flush the fuel lines to eliminate water contamination. Ignoring this issue may lead to expensive repairs down the line.

To prevent this, it’s essential to regularly check and change your car’s fuel filter and be careful where you fill up at gas stations. If possible, stick to reputable locations and avoid any that appear unclean or neglected.

It’s also a good idea to periodically check for water in the fuel, especially during seasons with higher rain chances. Keeping an eye on these things can save you from dealing with unnecessary headaches and costly repairs in the future.

Water In Gas Tank Symptoms

The following are common symptoms of water in gas tanks:

Sputtering or idling problems

This will sound like your car is having trouble starting or maintaining a steady idle. This happens because water does not combust appropriately and disrupts the proper air-to-fuel ratio in the engine. In an idle state, the engine may even shut off completely. 

Surging or sudden increase/decrease in power

Your car may feel like it’s struggling to accelerate or have a decreased gas mileage or sudden increase in power. This occurs because water disrupts the air-to-fuel ratio, making it difficult for the engine to combust gasoline appropriately. Misfires happen when the spark plugs do not ignite the fuel correctly, leading to a loss of power and decreased performance.

Rust in the gas tank

Usually, the tank is coated with a protective layer to prevent rust, but water can begin to break down this coating and lead to visible rust in the gas tank. In extreme cases, this can even cause holes and leaks in the tank. This will eventually allow even more water to enter the fuel system and worsen the previous symptoms.

Poor fuel economy

A more obvious symptom but water in the gas tank will decrease overall fuel efficiency as it does not combust properly and can clog up fuel filters. At the same time, you might not notice immediately, but over time, the decrease in fuel economy will add up and cost you more money in gas. 

Also Read: Bad Fuel Pressure Regulator Symptoms

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The car refuses to start.

Last but not least, if ignored or left untreated, water in the gas tank can eventually lead to your car not starting. The engine cannot combust any fuel appropriately and will not have enough power to turn on.

In this case, having a professional drain the gas tank and flush out the contaminated fuel is best. 

Also Read: Bad Fuel Pressure Regulator Cause No Start

Causes How There’s Water in the Gas Tank 

Reasons for water in the gas tank can vary, and there is no one clear-cut answer. Here are some possible explanations:

Broken or lousy fuel cap

Just by simple examination, you should be able to see if the seal on your fuel cap is cracked or damaged. A broken seal can allow water to enter the gas tank and mix with the fuel, leading to the abovementioned symptoms.

Bad top fuel pump

A broken or malfunctioning fuel pump can also lead to water entering the gas tank. Usually, the fuel pump is meant to filter out any water and keep it from mixing with gasoline. It may allow water to pass through and contaminate the fuel supply if not functioning correctly.

Contaminated fuel

Although rare, water can enter the fuel supply at gas stations or during the transportation of gasoline. This can often happen during heavy rain or flooding when water might mix with the gasoline leading to contamination in multiple gas tanks.

How To Remove Water In a Gas Tank 

To remove water in the gas tank, it’s best to consult with a professional mechanic who can drain and flush out the contaminated fuel. However, should you decide to attempt it yourself, here are some steps to take:

1. Drain the fuel from the tank into a separate container.

2. Rinse the gas tank with a water and fuel additive mixture to remove any remaining water and contaminants. 

3. Refill with clean fuel and properly seal the gas cap to prevent future contamination.

It’s important to note that attempting this process on your own may cause damage to your car if done incorrectly, so proceed with caution or leave it to a professional mechanic. Fixing any underlying issues, such as a broken fuel pump or faulty gas cap, is crucial to prevent future contamination. 

And, of course, always remember to periodically check for water in the fuel and address the issue as soon as possible to avoid worsening symptoms and damage to your car.

Frequently Asked Questions 

Can water in the gas tank damage the engine?

Yes, water in the gas tank can damage the engine as it does not combust appropriately, leading to clogging or malfunctioning of the fuel system.

How long does it take for Heet to remove water?

It can vary, but typically it takes around 20-30 minutes for the Heet fuel additive to dissolve any water in the gas tank. However, it’s important to note that this should not be used as a long-term solution, and any underlying issues causing contamination should also be addressed. 

Can HEET damage your car?

Used as directed, HEET should not damage your car. However, it’s essential always to follow the instructions on the product and consult with a professional mechanic if unsure. 


Water in the gas tank can lead to various car troubles and should not be ignored. It’s important to periodically check for water contamination and address any underlying issues causing it.

Consult with a professional mechanic if you are unsure how to remove water from the gas tank or encounter any severe symptoms such as engine malfunction. Always remember to properly seal the gas cap and use fuel additives as needed to prevent future contamination.

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