If you have read our article Why are my Fuel Filters Blocked? you are probably wondering how you can easily and simply remove water and other contaminants from your fuel to stop the dreaded diesel bug taking hold.
Water comes from the supplier, insecure tank fittings and the atmosphere in the form of condensation. Let's look at these three ingress points.
The Supplier? Fuel changes hands, and tanks, as much as 7 times before you, the end user, receives it. After refining it is stored, transported and transferred each time the fuel is traded. Be that in tanks on ships, barges or road tankers to finally being received into your tank at each point the fuel picks up contaminates in the form of debris and the biggest contaminant; water. The debris can easily be filtered out but the water is more difficult to remove so can often end up in your tank.
Insecure Tanks Fittings? Although self explanatory we hear a lot of stories of water in tanks that after investigation has come from loose filler caps, perished or missing gaskets, broken tank breather pipes, sounding pipes etc etc.
Condensation? As the tank heats during the day and cools at night the fuel expands and contracts expelling air and drawing it back into the tank, This moisture laden air readily condenses on the tank wall and falls to the bottom as free water. It is insidious, a very small amount every single day, worse on some days better on others but non the less it very very slowly builds up on the bottom of the tank. this is made worse If the fuel contains Bio-Diesel (FAME). BioDiesel is 30 times more hygroscopic than standard diesel meaning it readily absorbs water from the atmosphere. depending on which country you are in, condensation is by far the biggest source of water.
What is so harmful about the water?
Water in the bottom of a diesel tank is by far the single greatest contaminant you will find and will quickly lead to many problems. Water accelerates the degradation of diesel, it forms a habitat for Diesel Bug, it reduces the lubricity in the fuel, it helps the agglomeration of asphaltenes. Rusts the tanks and fuel system and in extreme cases when absorbed in the fuel can turn to super heated steam and blow the top of the fuel injectors in even worse cases, where areas of the tank is stagnant and no oxygen is available a highly aggressive special bug (anaerobic bacteria) grows that allows sulphuric acids to form. This creates resins in the fuel adding to the sludge and can eat through 1/2 inch steel plate . The resins look like sand, can be almost as hard and can pass through filters wrecking fuel pumps.
The most common form of sludge in the tank will be from Diesel Bug, The generic name given to moulds, yeast and bacteria. Removing the water is the first step to ensuring this microbial infection is minimized. Be careful of using diesel bug treatments that come with an alcohol carrier. The alcohol absorbs the water into the fuel so that it can pass through the engine. That was fine a few decades ago but can cause serious damage in modern high speed common rail engines, the more common treatments are Enzymes, there is more information here on the difference between Enzymes Vs Biocides. The only real way to remove the bug is to kill it with a biocide as in DieselAid® B and remove the water with a Diesel Dipper®.
Water/sludge can easily be removed from the VERY BOTTOM of the fuel tank with a Diesel Dipper®