Standard test for Water: ISO 3733
Maximum Water content: 1%


Its effects depend on the capacity of the fuel treatment system - which if well dimensioned can cope with water in excess of this 1% max content all standards since and including ISO 8217:1996 have a good safety margin incorporated especially with regards to lower viscosity fuels. Problems generally arise with the injection systems. The situation is aggravated if the water is dispersed through the fuel but there are additives that can help and by using a combination of settling tanks, heaters, purifiers and filters can be extracted. With larger amounts consider:

  • Increase temperature in the settling tanks, the highest possible temperature (whilst keeping it below Flash Point) to optimise the settling process.
  • Draining bottoms frequently of settled water.
  • Run two separators in parallel as purifiers at reduced throughput.
  • Clean the separators more frequently than usual to avoid untreated fuel passing into the service tank.
  • Fully open all regulator valves in the fuel lines. Increasing engine output naturally agitates the fuel, increasing the internal movement and circulation of the fuel, thereby increasing dispersion.
  • The amount of water left in the service tank will indicate the success of the above.

Cat fines, being hydrophilic, are drawn to water and so removing water content will help to remove damaging residual particles from catalytic cracking.