How To Remove Water From Diesel Fuel [Simple] - Auto Chimps (2024)

All diesel holds some water, even if it’s a microscopic quantity.

Water in your diesel fuel tank could be a real issue (over time). It leads to microbial growth, which rots the metal away and could clog or damage injectors. Over time, it could even lead to a leak.

Thankfully, the amount of water in your diesel is almost always negligible. As well as having contaminated fuel, your car would need to sit motionless for a lengthy time before any damage starts being done.

Although water in diesel sounds terrible, and scientists have spent years trying to prevent it, it might not be.

There’s a vital difference to know here. The water in your diesel could be either “free water” or “water-in-fuel” (aka “water-in-solution”).

Water-in-fuel is normal and perfectly fine. Free water is an issue.

Let’s start with the guide now.

How Does Water Get Into Diesel?

Diesel is a blend of hydrocarbon chains (and additives). It’s refined from crude oil and many other things like gasoline and kerosene.

The refining process isn’t 100% effective. Nothing is. That means there will always be a small amount of contamination. In this case, it’s water.

All diesel holds a tiny percentage of water. Standard low-sulfur diesel holds up to 0.1%. Biodiesel is a larger offender, harboring up to 1% water.

It might not sound like much. And it isn’t. This is water-in-fuel, and your engine has been designed to accommodate it. It will fire into the cylinder as vapor and burn off with the diesel.

Free water (liquid) would, however, be a worry. You need to watch for excess water from your tank to the fuel filter through the fuel lines. It’s here that rust could start to form.

Do I Have Water In My Diesel Car?

The issue doesn’t typically hit civilian passenger vehicles. That’s especially true if you fill up at a conventional gas station.

The regulations surrounding diesel quality are simply too stringent. For example, EU standard EN 590 allows for “200mg/kg of water” (0.02%). According to a Polish research paper, a typical range for water content in diesel is”0.003 – 0.100% (m/m)”. This is all water-in-fuel.

No matter what vehicle you drive, the most effective way to check your diesel for free water is to look at the fuel filter. Check your owner’s handbook to see where to find this.

Provided you haven’t driven for a day or so, the water will sink to the bottom. You’ll see it when you take the filter out. Be cautious not to spill the fuel.

There is no surefire way to inspect the water level in your fuel tank apart from using a testing paste on an elongated dipstick. Examining the fuel filter is a simpler task.

This issue typically affects vehicles in the construction, farming, or maritime industries.

These vehicles often fill up from above-ground tanks. These tanks are more susceptible to accumulate water over time. This water might unintentionally get pumped into their fuel tanks.

It takes a lot of fuel to create a water reserve large enough to start rusting. But vehicle fleets will easily get through thousands of gallons per year.

How To Get Rid Of Water In Diesel

As explained, excessive water in a passenger vehicle is very rare. It should only happen if you use unregulated biofuel in your tank.

You probably won’t know about free water in your diesel until a mechanic finds water in your fuel filter. In the meantime, you might get misfires due to impaired injectors (in severe cases).

Once the water’s in your tank, that’s that. You should drop the tank out of the automobile and cleanse it.

If substantial damage has already been done, you might even want to install a new tank. At the very least, antibacterial substances should be used to remove any traces of the rust- and gunk-creating microbes.

Free water might even have caused some serious engine damage.

It’s essential to trace the source. Water shouldn’t be in your tank, especially not in a new diesel vehicle. It’s more probable to come from an above-ground filling tank.

The overwhelming majority of any trace amounts of water in your diesel will mix into an emulsion (a temporary mixture). It’ll pass through your engine in small enough quantities to not do any damage.

Alternatively, you could use a diesel supplement. This won’t be a long-term fix for any rusting problems, though.

Additives To Remove Water From Diesel Tank

You might have heard of some additives that eliminate water from diesel (or gas). Some of the most prevalent are made by:

• CRC Diesel Dry
• Diesel Force HydroClean
• ISO-Heet Water Remover & Fuel Line Antifreeze

These don’t remove water, per se. The additives are often purified isopropanol (also known as isopropyl alcohol or rubbing alcohol). Other chemicals are added for supplementary benefits.

Isopropanol is a hydrocarbon chain with three carbon atoms. It bonds with the water (H₂O), capturing the molecules within its arrangement.

The water can now pass through the engine as part of the isopropanol. The water doesn’t turn into diesel (now there’s a maneuver that would be worth witnessing!) – but it’s now part of a flammable liquid.

The isopropyl alcohol hydrocarbon isn’t exactly ideal for your engine, but it’s much superior to water. Since it’s the same type of hydrocarbon as diesel, it mixes in with your fuel.

After pouring in the isopropanol additive, wait for a few hours. It descends to the bottom of the tank and chemically bonds with any water.

Ensure you add the proper ratio of isopropyl alcohol to water.

Can You Add Rubbing Alcohol To Diesel To Get Rid Of Water?

Make sure you buy a suitable additive.

This contains pure isopropanol. Rubbing alcohol off the shelf typically contains about 70% isopropyl alcohol and 30% water. The range can vary between 60% and 90% alcohol.

This is because strong alcoholic solutions do not provide significantly better anti-microbial outcomes. It is a waste of money, so drug companies add water to dilute it.

Therefore, adding a rubbing alcohol solution to your diesel tank actually adds more water. Well, if ever there were a pointless exercise…

Conclusion

In summary, this issue typically affects fleet vehicles’ filling tanks. It’s most probable to impact those that store diesel on-site without sufficient maintenance.

If you have an unusually high amount of free water in your car’s diesel tank, it probably came from one of these.

Diesel additives should be added to a storage tank to bond with unbound water. Do this pre-emptively – before the rust even has a chance.

If you find free water in a vehicle’s fuel tank, drop and clean it. If necessary, replace it.