How To Get Water Out Of The Gas Tank

Water in your gas tank is a problem that can range from a minor annoyance to a full-blown engine catastrophe. It's a common issue, especially in older vehicles or those exposed to fluctuating temperatures, and understanding how to deal with it is crucial for any DIY mechanic or experienced car owner. This article will delve into the causes of water contamination, the technical aspects of removing it, and best practices to prevent it from happening again.

Background: The Combustion Engine and Fuel System Vulnerabilities

To understand why water in the fuel system is so problematic, let's quickly review the basics of how an internal combustion engine works. The engine needs a precise mix of fuel and air to create combustion. This process happens in the combustion chamber, where a spark ignites the fuel-air mixture, driving the piston and ultimately turning the wheels. Modern engines, specifically those with fuel injection, rely on precise fuel delivery to each cylinder.

The fuel system is responsible for delivering that precise fuel. It typically consists of several components:

Fuel Tank: Stores the gasoline.
Fuel Pump: Draws fuel from the tank and sends it to the engine. Submersible fuel pumps are the norm.
Fuel Filter: Removes impurities from the fuel to protect the injectors.
Fuel Rail: Distributes fuel to the injectors.
Fuel Injectors: Precisely spray fuel into the intake manifold or directly into the cylinder (in direct injection systems).
Fuel Pressure Regulator: Maintains consistent fuel pressure in the system.

Water compromises this system in several ways. Firstly, water doesn't burn, disrupting the combustion process. Secondly, water can corrode fuel system components, leading to rust and damage. Finally, in cold weather, water can freeze, blocking fuel lines and preventing the engine from starting.

Technical Breakdown: How Water Gets In and How to Remove It

Sources of Water Contamination

Water gets into the gas tank primarily through:

Condensation: Temperature fluctuations cause condensation inside the tank, especially when it's not full. The air contains moisture, and as it cools, that moisture condenses into water.
Contaminated Fuel: Occasionally, fuel stations may have water contamination in their storage tanks. While rare, it can happen.
Loose Fuel Cap: A damaged or loose fuel cap allows moisture from rain, car washes, or even humid air to enter the tank.

Removing Water: The Technical Process

Here's a breakdown of several methods to remove water from a gas tank, ranging from simpler to more involved:

Fuel Additives (Water Removers): These are chemicals designed to absorb water and allow it to be safely burned along with the fuel. Most contain alcohols like isopropyl alcohol or ethanol, which are hydroscopic (meaning they attract and absorb water). This method is most effective for small amounts of water. Follow the manufacturer's instructions on the additive bottle. The alcohol helps to emulsify the water so it can pass harmlessly through the fuel system. It's important to note that excessive use of alcohol-based additives can damage rubber components in older fuel systems, so use them sparingly.
Fuel Drain Plug (If Equipped): Some older vehicles have a drain plug at the bottom of the fuel tank. Locating this plug (consult your vehicle's service manual) allows you to drain the tank and remove the water, which, being heavier than gasoline, will settle at the bottom. Be extremely careful when working with gasoline, as it is highly flammable. Have a suitable container to catch the fuel, and work in a well-ventilated area away from any sources of ignition (sparks, open flames, etc.). Afterwards, properly dispose of the contaminated fuel according to local regulations.
Siphoning: Siphoning involves using a hose to drain fuel from the tank. This is a viable option if there's no drain plug or if you need to remove a significant amount of fuel. Insert one end of the hose into the tank, making sure it reaches the bottom. Create a siphon by sucking on the other end of the hose (using a siphon pump is much safer and recommended!) and then quickly placing that end into a container lower than the fuel tank. Let the fuel drain until you've removed as much as needed. Again, be extremely cautious with gasoline and ensure proper disposal.
Removing and Cleaning the Fuel Tank: This is the most thorough but also the most labor-intensive method. It involves disconnecting the fuel lines, electrical connections, and mounting straps, and then carefully removing the fuel tank from the vehicle. Once removed, you can thoroughly drain and clean the tank. Inspect the tank for rust or damage while it's out. Allow the tank to air dry completely before reinstalling it. This method is recommended if you suspect significant contamination or rust within the tank. Be sure to replace any worn fuel lines or connectors during reassembly.
Using a Fuel Sample Port or Line Disconnection to Check for Water: Many modern vehicles have a schrader valve or fuel sample port on the fuel rail that allows fuel to be drawn. Carefully relieve the fuel pressure by disconnecting the fuel pump relay and then attempting to start the car. Once the car is stalled, you can either loosen a fuel line or use the fuel sample port to drain a small amount of fuel into a clear container. Let the sample settle. If there's water present, it will separate and settle at the bottom of the container. This is a quick way to diagnose water contamination without draining the entire tank.

Drying the Fuel System After Water Removal

After removing the bulk of the water, it's crucial to dry the fuel system to prevent further corrosion. Using a fuel system dryer additive is a good step. You can also crank the engine (without starting it) for short bursts to help purge any remaining water from the fuel lines and injectors. Be cautious not to overheat the starter motor during this process.

Common Issues and Maintenance Concerns

Clogged Fuel Filter: Water and debris can clog the fuel filter, restricting fuel flow and causing engine performance problems. It's a good practice to replace the fuel filter after removing water from the tank, especially if the contamination was significant.
Corrosion: Water can corrode metal components in the fuel system, leading to rust and eventual failure. Regular fuel system maintenance and the use of fuel stabilizers can help prevent corrosion.
Injector Problems: Water can damage fuel injectors, leading to poor fuel atomization and misfires. In severe cases, the injectors may need to be professionally cleaned or replaced.
Frozen Fuel Lines: In cold weather, water in the fuel lines can freeze, blocking fuel flow and preventing the engine from starting. Using a fuel additive with anti-gel properties can help prevent this.
Check Engine Light (CEL): Water contamination can trigger the check engine light, often with codes related to misfires, lean fuel conditions, or fuel pump performance. Always diagnose the underlying cause of the CEL before simply clearing the code.

Do's and Don'ts / Best Practices

Do's:

Use a fuel stabilizer: Fuel stabilizers help prevent fuel from degrading and can also protect against water contamination.
Keep your fuel tank full: A full tank reduces the amount of air inside, minimizing condensation.
Replace your fuel cap if it's damaged or loose: A properly sealed fuel cap prevents moisture from entering the tank.
Purchase fuel from reputable stations: Stations with high fuel turnover are less likely to have water contamination.
Change your fuel filter regularly: A clean fuel filter helps protect your fuel injectors and engine.
Use appropriate safety precautions: When working with gasoline, wear safety glasses and gloves, work in a well-ventilated area, and avoid any sources of ignition.

Don'ts:

Ignore warning signs: If you notice symptoms of water contamination (e.g., rough idling, stalling, poor performance), address the issue promptly.
Use excessive amounts of fuel additives: Overuse of additives can damage fuel system components.
Smoke or use open flames near gasoline: Gasoline is highly flammable and can cause serious injuries or death.
Dispose of contaminated fuel improperly: Dispose of gasoline according to local regulations.
Neglect regular maintenance: Regular fuel system maintenance can help prevent water contamination and other problems.

Conclusion

Water in the gas tank is a serious issue that can lead to a variety of engine problems. By understanding the causes of contamination, the technical aspects of removal, and best practices for prevention, you can keep your fuel system healthy and your engine running smoothly. If you're comfortable with basic automotive repairs, you can attempt to remove the water yourself using methods like fuel additives or siphoning. However, if the contamination is severe or you're not comfortable working with fuel, it's best to consult a qualified mechanic for professional assistance. In the long run, preventative measures, such as using fuel stabilizers and keeping your fuel tank full, are the best way to avoid this problem altogether.