Water in Your Underground Storage Tank
Written by: Brian Pottebaum, Director of Training Services
An angry customer walks into your store saying they just filled up here and now their car won’t run. A quick look outside shows that another car has stalled trying to leave your parking lot. Your customers have just pumped water from your tanks into their gas tanks! Hopefully this has never happened to you, but are you still taking steps to ensure that it doesn’t happen?
Bad gas claims are a nightmare. But what might be even worse is having water in the UST and not knowing the reason. Where is the water coming from? Is your UST leaking? Is the water harboring microbes or damaging the inside of your tank?
How do you know if you are getting water in the UST?
Obviously, the angry customer is one way to find out, but there are better ways to monitor and prevent it.
Product inventory records are more efficient and less expensive for finding water in your petroleum storage tanks before your customers find it in theirs. Daily inventory review will help you keep track of fuel throughput as well as water intrusion. Water accumulation in the tank can be an indicator of a potentially bigger problem like a leaking tank system – finding a leak early will save you a headache and a large bill. You can learn more about inventory control in a document that was published by EPA and is available at https://www.epa.gov/sites/default/files/2014-03/documents/inventry.pdf
If you have an automatic tank gauge or ATG (and about 98% of UST operators do), does the tank monitor indicate water in the tank? If you stick the tank for fuel measurements, are you checking for water? You should apply a water-finding paste to the bottom 3 to 4 inches of the stick to check for water once a month. Because water is heavier than fuel, it will collect at the bottom of the tank, so it is very important that the stick reaches the bottom when checking for water. Contact your service company for the correct indicator paste, as it depends on the type of fuel in the tank, especially if you are storing higher percentages of ethanol.
Most facilities use an electronic tank monitor (such as an ATG) to collect this information, rather than manually sticking the tank. These monitors generally provide a printout indicating fuel levels as well as water if present. Every day someone should be reviewing these printouts. They are typically set to alarm if the water level exceeds 1 inch in the fuel tank. Water levels between 1 and 2 inches require immediate attention, and if levels exceed 2 inches it is advised that you take the tank out of service until the issue is addressed. All tank monitor readings should be verified with actual stick measurements using water-finding paste. If possible, measurements at both ends of the tank should be conducted, because the tank could have been installed with tilt from one side to the other. This could mean that water will register on one side of the tank, but if there is enough tilt, it will not appear on the other side of the tank.
Additionally, more consideration must be applied when the fuel tank contains a higher blend of ethanol, because water will bond to the ethanol and result in a phase separation layer that will not register on the standard ATG probe.
What causes water to get into tanks?
If you have more than 1 inch of water in your tank, we encourage you to contact your service company to assist you in troubleshooting this problem. Condensation inside the tank can cause some water to develop, however it typically is not problematic. Other ways water can enter the tank is by loose fittings and caps on the tank-top, leaking drain plug in the delivery spill basin, damaged vent line draining water back to the tank, water in the fuel transport delivery, or, worst-case scenario, a tank with one or more holes in it. In all cases, you must detect the problem as quickly as possible to determine the source and correct the problem.
How should you remove water accumulation?
Once you have determined that water has accumulated in your UST, work with your service company to remove the water safely and appropriately from the tank. Remember that this is a hazardous substance, and it must be handled and disposed of in accordance with state and federal regulations.
Why should you be concerned about water in the tank?
Aside from the issues mentioned above, water in the tank can affect the quality of your fuel, especially when blended with ethanol. Although fuel will generally have small amounts of moisture in it, the amount is not enough to cause noticeable performance issues for your customers. However, you want to prevent the moisture from accumulating in the tank, so constant monitoring is necessary. Tanks with higher throughput are typically the outlier since there is little time for water to settle out and accumulate at the bottom. Even small quantities of water accumulation in ethanol-blended fuel may cause phase separation resulting in a water-ethanol mixture at the bottom of the tank. Higher ethanol blends have even less tolerance for water. When fuel is drawn from the tank by either suction or pressurized delivery to the dispensers, it is pulled from the bottom of the tank. Therefore, you can see the potential problems with water accumulating in the tank, even if it is only 1 inch deep!
If you discover that your tank is leaking, please remember to report the incident immediately to your insurance company and the regulatory agency. Regulations require that you report a suspected petroleum release within 24 hours of discovery. It is critical that the issue be addressed as quickly as possible to minimize damages.