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Water and ethanol blends


Q: Is water contamination in gasoline a big problem in Minnesota?
A: No. The vast majority of stations in the state will never experience any water contamination in their product.

Q: How do you know if there is water in a station's gasoline?
A: Water is heavier than gasoline and, if present, will settle to the bottom of a storage tank. Environmental regulations require new storage tanks to be equipped with electronic sensors which alert the station operator if water is present.

The Department of Commerce Weights and Measures Division tests stations' storage tanks for water during its routine inspections. Tanks containing a gasoline/ethanol blend absorb water which may not be detected by either the tanks' sensors or the Weights and Measures investigator. Ethanol acts very much like the Isopropynol some people add to their vehicles' gas tanks in the winter. It absorbs the water and prevents gas line freeze. In small amounts, water in a gasoline/ethanol blend will not affect a car's performance.

Q. If water might not be detected, what prevents station owners from "watering down" their gasoline/ethanol blends?
A: Common sense. Gasoline/ethanol blends cannot absorb unlimited amounts of water. The amount they can absorb without causing customer problems depends on the volume of product, the percentage of ethanol, the temperature of the station's in-ground storage tank, the temperature of the customer's gas tank, and the amount of ethanol already in the customer's gas tank.

It would be almost impossible for station owners to water down their product and be sure that none of their customers would experience car problems. Station owners are liable for repairs if they sell water contaminated gasoline. They may also be subject to criminal prosecution if they are intentionally adding water to their product. Most station owners want to avoid those consequences and maintain a good reputation with their customers.

In addition, the Weights and Measures Division regularly samples diesel fuel and gasoline around the state and analyzes them in its laboratory. Laboratory tests can detect even small amounts of water in gasoline/ethanol blends. Station operators are usually happy to be informed of any water found so that they can take corrective action before it causes their customers problems.

Q: If station operators do not intentionally water down their product, how does water get into a station's storage tank?
A: Ground water may seep in through cracks in older storage tanks; or rain or snow might get in through a cracked, poorly fitted, or improperly applied cap on the fill pipe. Environmental regulations for up-grading old tanks and installing new ones are eliminating these problems.

Q: If ethanol absorbs water, how can you have water contamination in a gasoline/ethanol blend?
A: A gasoline/ethanol blend can absorb a certain amount of water. In general, the greater the percentage of ethanol in the blend, the larger the amount of water the blend will hold. Also, the higher the temperature, the greater amount of water the blend will hold. A blend that contains the maximum amount of water it can absorb for that temperature and percentage of ethanol is saturated.

If a saturated blend drops in either temperature or percentage of ethanol, the water will start to precipitate (fall) out of the solution and settle at the bottom of the tank. This water will be mixed with ethanol since ethanol bonds more easily with water than gasoline. The gasoline mixture at the top will still be saturated. It will continue to precipitate out a water/ethanol mixture as the percentage of ethanol drops until there is either no more water in the gasoline, or another saturation point is reached (if the temperature is rising at the same time, for example). This is what is referred to as a phase separation. A phase separation can occur in a storage tank or in a vehicle's gas tank. As soon as water/ethanol begins to precipitate out, an in-ground tank's sensors will be able to detect its presence and signal the operator that there is a problem.

Q: What happens if people buy phase-separated gasoline?
A: If a phase separation occurs in a station's storage tank, the customer may get either gas/water/ethanol, gas/ethanol, or water/ethanol depending on the degree of separation, and the height of the water/ethanol phase in relation to the discharge pipe leading from the tank to the dispensers.

Q: Will everyone who buys phase-separated gasoline experience car problems?
A: Fortunately, no. Very few people usually experience problems. Many people buying a water-saturated product will still have some unsaturated gasoline/ethanol blend in their tanks. Most people's gas tanks are often warmer than stations' in-ground storage tanks during the spring, summer, and fall months. This means that a blend which is saturated in the ground will no longer be saturated in the car's tank. In a few rare cases the water/ethanol phase in a contaminated tank may reach the level of the tank's discharge pipe. Usually a phase separation is detected and corrected long before this is the case. Any customer who purchases part of the water/ethanol phase will experience difficulties immediately.

Q: How does a station operator remove the water from a phase-separated blend?
A: The best way to correct a water problem in an ethanol/gasoline tank is to drain the tank completely and replace it with uncontaminated product. An alternate method is to remove the ethanol/water mixture from the bottom of the tank and then wait 24 hours. The product CANNOT be sold to the public during this time. If more ethanol/water precipitates out, the operator must remove it from the tank and wait another 24 hours.

If no more ethanol/water precipitates out, the tank may be `topped off' with a mixture of ethanol and gasoline. It is very important to contact the Weights and Measures Division when using this method since the quantities of ethanol and gasoline added will depend on the size of the tank, the amount of the product remaining, and the amount of ethanol removed from the original blend. When the Weights and Measures Division determines that the product in the tank meets all octane and oxygenate requirements, the product may again be put up for sale to the public. The operator then contracts with a licensed hazardous waste carrier to transport the ethanol/water mixture which was removed from the bottom of the tank. The hazardous waste operator must dispose of the ethanol/water mixture in accordance with environmental regulations.

Q: What should I do if I suspect I have purchased water contaminated gas?
A: Drain your tank and change your fuel filter. This is extremely important for carbureted vehicles since water can damage the carburetor. If the gasoline appears cloudy, or if it separates into visible layers, it probably contains water. Contact the station operator. (A canceled check or receipt to show when you purchased the gasoline is useful.) Most operators will be happy to work with you if the contaminated product came from their station.

If the operator is sure that the station's product is not contaminated with water, contact the Weights and Measures Division (612-215-5821). An investigator will be sent out to test the tanks and to collect samples for laboratory analysis. Make sure to call the Division as soon as possible. Most stations receive fuel shipments several times a week. It is best if the investigator can collect samples before another shipment has arrived. The investigator will contact you with the test results. In some cases the investigator may request a sample of the gasoline you drained from your tank.

If the station's product was not contaminated with water, the problem may lie with your vehicle tank. Tanks which are allowed to sit empty over the winter, or tanks with missing or improperly fitting gas caps may collect water. Keeping your gas tank full in the winter months and making sure that your gas cap is tight can reduce this problem. Remember, a rag stuffed into a fill pipe acts as a wick for moisture; it will not keep water out of your tank.