Water and gas have different densities and they won't mix. If you have ever been unfortunate enough to have water inside your petrol tank you will know that this is not any good news when the word fuel filter is mentioned. If you a have car that cannot filter water automatically from fuel then your fuel injectors will be damaged. There are several reasons why you may have water in gas tank, but first, we will look at how it affects the engine and what methods you can use to detect its presence in fuel tank.


How Water Gets In Gas Tank​?

By default, there is a negligible amount of water in your fuel. However, for substantial amount of water to find its way into the gas tank to the extent of stalling your car, the sources of water have to be big.

Condensation as a result of fluctuating temperatures may bring in more water when fuel thaws.

Some fuel types like diesel have a high affinity to water, leaving your gas tank open attracts air moisture into the gas tank.

You may fail to believe me but if you are unlucky you may end up buying fuel already contaminated by water from the filling station. Or your car wash attendant accidentally pours water into the tank when the gas lid is open or not properly closed.​

How To detect Water in Gas Tank​?

There are two ways that you can tell if you have water in your tank. One method is paying attention when driving. The other method is by doing a routine oil fuel check using water finding paste.​

Through Driving​

The obvious symptoms that you can get from a car that has its fuel mixed with water is the slow pick upon acceleration, the car may suddenly jolt when driving at high speed, and a lot of noise will come from the engine.​

These are the clear signs that you have water in gas in tank, this sluggish behaviour is caused by water being sucked up the fuel injectors instead of fuel. This forces the injectors to spray water in the combustion chamber which is then turned into steam and this explains why you are slowing down instead of accelerating.​

Water Finding Paste​

The other way of checking the level of water in gas tank is by making use of a special paste that you apply on the tank stick and push the stick to the bottom of the fuel tank. Look at the height of discolouration on the stick. Depending on how high or low the mark is.​

Fixing the Water Problem​

It is normal to have a small percentage of water in gas tank but not to the extent of interfering with your fuel distribution system. But if you suspect that your gas tank has a substantial amount of water this is what you need to do.

Empty the Gas Tank​

If you don’t resolve the water problem soon enough you will end up with a rusted fuel system. The immediate solution would be to flush the tank and refill with fresh fuel. While this may seem feasible it may not apply to everyone due to economic reasons. If you decide to empty the fuel tank, leave it for some time to dry before refuelling. There are other simpler solutions that you can use to “dry” the fuel.​

Use of Drying Agents​

There are some fuel additives in the market whose sole purpose is to drain or suck up water from fuel. They act like drying agents whose work is to separate water from fuel and drain away. The good thing about using these additives is that they slow down the freezing of fuel during winter, and prevent rust from building up due to the presence of water in the gas tank. What you need to know is that fuel drying agents cannot be effective when there is a lot of water in gas tank.


Water in gas tank will certainly ruin your day if you had plans for a long journey. To avoid this problem it is always recommended that you regularly check the water levels in your gas tank. This inspection is best done after winter when thawing is just setting in. However, some engines have filters that are capable of separating water from fuel but they may not always be as effective as putting up preventive measures to make sure no water gets in gas tank.

Now that you know the effects of water on your fuel injectors, I am sure you do not want to see your friends go through the rigours of replacing these engine components. Share this article so that they also get to know the effects of water in gas tank, how to detect water, how to prevent future problems, and crucially they get to know how water gets in gas tank.​

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Chief editor at Paul's Gigantic Garage. I came up with this blog to help you to sort out some basic problems your car may be facing and in turn, save lots of cash by some of my DIY tips that I hope will get your car out of its current situation. I also had in mind motor enthusiasts who for the love of cars who are constantly looking for information about cars on the latest trends, questions, fixes, driving, tricks, and accessories.


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