How To Remove Water From Diesel Fuel
When fuel testing confirms a problem, you have three main paths forward. Polish the fuel. Clean the tank. Pump it out and replace it. Most real situations call for some combination of the three.
Fleet Core are the fuel experts that can help you decide which path fits your situation. The right choice depends on what’s wrong with the fuel, what shape the tank is in, how much downtime you can afford, and how soon you need the equipment running again.
The Four Main Methods for Removing Water from Diesel Fuel: Polishing, Cleaning, Replacement, Additives
Each approach solves a different problem. Mixing them up wastes money and time.
Fuel polishing removes water, particulates, and microbial contamination from the fuel itself. It runs the fuel through filtration and separation equipment, returning cleaned fuel to the tank. Polishing works best when the fuel is salvageable and the tank is in reasonable condition.
Tank cleaning addresses the inside of the tank. Sludge, biofilm, rust, and accumulated debris on tank walls and bottoms get removed mechanically. Tank cleaning is necessary when the tank itself is the contamination source.
Diesel fuel additives with water emulsifiers can convert water into microscopic water droplets. In some situations, this can allow you to continue to run the fuel out and then replace it with fresh clean fuel.
Pump-out and replacement removes all the fuel and replaces it with fresh product. This is the right call when fuel has degraded past recovery, when oxidation has dropped cetane too far, or when the contamination is too severe for polishing to handle economically.
These four approaches can often work in sequence. Polish the fuel first to extend the time you have to plan. Clean the tank to stop the contamination at its source. Use fuel additives to treat small amounts of existing water-contaminated fuel. Replace the fuel when polishing won’t bring it back to spec.
Fleet Core helps Colorado businesses recover and PREVENT fuel contamination through thorough and cost-effect maintenance.
Common Ways That Water Gets Into Your Diesel Fuel
Fleet Core provides diesel fuel testing, polishing, and tank maintenance for businesses across the Colorado front range.
Natural Atmospheric Changes (Condensation)
This is the most common entry point for water in your diesel fuel. Every diesel tank breathes. As temperature swings through the day, air moves in and out through the vent. Warm, moist air enters during the day. As the tank cools overnight, that moisture condenses on the tank walls and drips down into the fuel. Colorado’s Front Range sees wide daily temperature swings, especially in shoulder seasons, which makes condensation a bigger factor here than in climates with flatter temperature curves.
Tanks with low fuel turnover condense more water than tanks that get used and refilled often. A generator tank that sits at half capacity for months has more empty headspace to condense moisture into than a tank that’s cycled weekly. This is counterintuitive. Fleets often assume their least-used equipment has the cleanest fuel. It’s usually the opposite.
Pre-Contaminated Fuel Added To Your Tank
Sometimes water is already in the fuel before it reaches your tank, picked up in the supplier’s storage tank or during transport and hauling.
Fuel Tank Failure
Cracks, corroded seams, or pinholes in the tank shell let rainwater or groundwater seep in directly. Older underground tanks are the most common case.
Damaged Fill Caps, Gaskets, or Vents.
A cracked gasket, a loose fill cap, or a poorly installed vent gives rainwater a direct path in.
Delivery and Transfer Contamination.
Hoses, fittings, or transfer equipment carrying residual moisture from a prior use can introduce water during fueling.
Is it easy to tell if there is water in my diesel fuel?
This can be a bit of an “it depends” answer.
When you have so much water in your system that you can clearly see it in your fuel water separator, then yes, it is easy to spot.
However, there are actually three ways that water can exist in your diesel fuel: free, emulsified, and dissolved.
The ways in which water exists in your diesel fuel will determine how easy, or hard it is to identify and remove.
Water Freely Suspended
Free water settles to the bottom of the tank because it’s denser than diesel and doesn’t mix with it. This is the water you’ll find in a water separator, on a water-finding paste test, or see pooled in a sample drawn from the tank bottom. It’s the easiest form to detect and the easiest to remove.
In some cases, fuel additives with emulsifiers can be used to turn freely suspended water into microscopic water droplets. The water-contaminated diesel can then be ran through the equipment.
Emulsified Water
Emulsified water is suspended as tiny droplets throughout the fuel instead of settling out. Agitation from pumps, fuel movement, and certain fuel additives can emulsify free water that would otherwise have settled. Emulsified water is what gives contaminated fuel a hazy or cloudy appearance. It’s harder to remove than free water but still recoverable through filtration and coalescing during polishing.
Dissolved Water in Diesel Fuel
Dissolved water exists at the molecular level, similar to humidity in air. Diesel fuel can hold a small amount of water in dissolved form without it causing problems, and this water doesn’t settle out, emulsify, or show up as haze. Polishing doesn’t remove dissolved water, and normal ASTM specifications account for it. Dissolved water is not the water contamination problem fleets need to worry about. Free and emulsified water are.