Proper Storage of ULSD in Fuel Storage Tanks

ULSD (ultra-low sulfur diesel) is a bio-fuel that has become common in recent years both due to regulatory requirements as well as for its cleaner-burning, more efficient characteristics. Storing any fuel requires proper management, and this especially true in the case of ULSD. This bio-fuel is highly vulnerable to water contamination, even more so than other fuels. As such, it’s important to take steps to prevent the buildup of water in the fuel storage tank, as well as to know how to detect the presence of water in the tank. Learn more in our blog on proper storage of ULSD in fuel storage tanks.


Proper storage of ULSD is critical for the integrity of the fuel.

Storing ULSD

The Effect of Water on ULSD

Water does not mix with the fuel, instead forming a thin layer around it. Microbes live where the fuel and water meet, and eat the organic compounds in the bio-fuel. This degrades the fuel, which can cause problems both in the storage tank and in vehicles that use the fuel. This includes:

  • Clogged filters.
  • Accumulation of sludge.
  • Pump and injector problems.
  • Malfunction of the water monitoring system.

In addition, if salts are present in the water in the tank, they can alter the chemical structure of the fuel, damage the tank, and potentially cause a leak.

How does water get into fuel storage tanks?

  • Leaks due to damaged components of the delivery system.
  • Condensation.
  • At the refinery/during transport from the refinery to the tank.
  • Inadvertent drainage of spill buckets into the tank.
  • Stormwater runoff.

What are the signs of water in a ULSD tank?

The following are caused by microbe growth.

  • The smell of sulfur in the fuel or filter.
  • Corrosion of metal filter/irregularity in filter covering.
  • Inversion rag layer in tank bottom sample.
  • Spotted water coalescing the filter.

The next signs are caused by the formation of solids/semi-solids in the fuel.

  • Corrosion – presence of a red-orange silt.
  • Degraded fuel – brown/black particulate matter.

General symptoms also include:

  • Failure of system components.
  • Clogged fuel lines.
  • Inconsistent gauge readings.

How to check a storage tank for water contamination.

ATG systems are the standard for monitoring water in a ULSD tank, but it’s important to compare the reading from the ATG with manual gauge readings to look for inconsistencies that suggest water in the system. In addition, use the following guidelines when taking samples:

  • Do take multiple samples from different locations. Good ones include the low end of the tank, and from under the submersible turbine pump.
  • Do not take samples from the fill tube.

How to prevent water contamination in ULSD tanks.

Preventing water contamination starts during delivery.

  • Compare water gauges before and after fuel delivery.
  • Check fill and gauge caps for tightness after delivery.
  • Check system again after fuel has been allowed to settle.
  • Use nominal 5 micron filter installation on fuel dispensers.
  • Remove debris and water around tank openings before delivery.

Other maintenance should include:

  • Daily inspections of all tank components for leaks or damage.
  • Use of cap and screen vents.
  • Regular monitoring of water levels.
  • Removal of water if it is greater than one inch.
  • Monthly fuel tank testing.
  • Follow manufacturer’s recommendations.

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This entry was posted on Wednesday, May 6th, 2015 at . You can follow any responses to this entry through the RSS 2.0 feed. Both comments and pings are currently closed.