Do-It-Yourself Fuel Tank Cleaning

Posted by Darrell Nicholson at 01:40PM - Comments: (12)

PS tested additives for their ability to prevent biological growth.

It’s usually this time of year that fuel contamination rears its ugly head, clogging filters right when we need our engine most. We’ve published several articles on preventing and coping with contaminated diesel fuel—ranging from additives, to fuel-polishing systems, to professional fuel-polishing services—but for some people, none of those remedies will fix the problem, and the only recourse is a thorough tank cleaning. Depending on the size of your fuel tanks, having a professional clean your tank and dispose of the dirty fuel can cost more than $1,000. But, for the careful, competent do-it-yourselfer, there is another option. For those sailors whose tanks have reached the contamination point-of-no-return, here’s a helpful article on DIY tank cleaning that accompanied our July 2009 test of diesel biocides.

There’s no getting around it; once filters begin clogging repeatedly, no additive or treatment applied to the tank will make the solids go away. The only realistic path to a clean tank is manual cleaning. It is commonly assumed this is a job for professionals, or a job that is extremely messy or dirty; that need not be true. Every tank is different; the resources and capabilities of each would-be do-it-yourselfer are different, but the following list of precautions and general guidance should keep you safe and minimize the mess and pain.

Burn the fuel down first. While it is certainly possible to pump all of the fuel out of the tank, a lot of pumping and hauling will be involved. Just like putting off going to the doctor, don't wait until the problem is fatal. Take your medicine early, burn the fuel out, and clean the tank.

Access. Hopefully the tank is fitted with a sufficient access opening. Although it is certainly possible to add a larger opening to a tank, the safety precautions involved are beyond the scope of this article and a professional should be engaged. Do not simply cut into an empty tank with a saber saw—the heat from cutting can generate enough fumes cause a fire or explosion. Additionally, the access hole must be sealed in a manner compliant with the appropriate code. It may be possible to clean the tank through the existing openings with some ingenuity.

Pumping. Although diesel fuel is not a flammable liquid, flammable mist can be generated by excessive agitation. The use of a shop vacuum is dangerous and has been linked to several fires. The safest pump is a manual bilge diaphragm pump, and most common brands are equipped with nitrile and neoprene elastomers that are compatible with diesel fuel; logically, since fuel and oil in the bilge is not unheard of. Head pumps are also so equipped. Any electrical pump should not be located in a confined space where vapors can accumulate.

Overflows. Be certain a person is stationed at each end of the pumping operation, and that one of these people can stop the pumping. It's surprisingly easy to lose track of time and overflow the receiving container. If siphon is possible, have a ready means to stop this.

Solvents. Some have suggested wiping down the inside of the tank with solvents in order to remove the last bit of residue. Clearly, this can be an extremely dangerous practice because of the flammable atmosphere the hazardous breathing atmosphere that can be generated. If you plan to wipe down the inside of the tank, a rag moistened with diesel fuel is the safe choice. An aqueous degreaser such Simple Green may also be useful, but it will be necessary to remove all cleaning residue.

Power washing. In many tanks, baffles or limited access openings will make it impossible to reach all portions of the tank. The professional tank cleaner’s solution is to use a power washer. The accessible portions of the tank will be washed down using an ordinary fan tip, though the end of the lance may be bent somewhat to improve access to the tank roof.

To reach more remote portions of baffled tanks, a tank cleaning nozzle capable of spraying in all directions is used. Several varieties of tank-washing nozzles are available from suppliers such as McMaster Carr. Though only rated at 100 pounds per square inch (psi), a typical power washer does not have the flow to produce over 40 psi pressure. One of the leading manufacturers of tank cleaning nozzles is Lechler, who offer a variety of designs to suit narrow openings.

The nozzle is attached to the end of a short piece of pipe (1-foot by ½-inch schedule 40 steel is typical); this is critically important to provide stiffness and to prevent the hose from turning back on itself and coming back out of the tank access hole, much like a snake crawling back up the arm of the handler. This stinger is attached to the length of flexible hose (3-10 feet of the same hose that the power washer lance is fed with), which is then attached to the tip of the power-washing lance in place of the usual nozzle. This extension is fed through the baffles in the diesel tank and will reach all areas. The tank cleaning nozzle/stinger is fed by hand and water flow must not be triggered until the nozzle is well inside the tank; a second operator is needed to control the water flow through the lance.

Ideally, the lance should only be triggered when the nozzle is in position and separated from the operator by at least one baffle. The water, sludge, and fuel that is rinsed off will typically drain back to a low area under the access hatch and can be continually pumped out while the powerwashing is in process. Protective equipment during this sort of powerwashing includes heavy rubber gloves, a raincoat, and face shield. Although caution will keep the power washing nozzle in the tank while the water is on, high-pressure water can cause extremely nasty injuries. The following link describes possible hazards using more powerful equipment, but the illustration is valuable.

Disposal. The marina’s used oil collection tank should be able to accept the contaminated fuel heel; contamination with polymerization sludge or biological fouling will not present any problems for the used oil recycler. Contamination with gasoline or solvents is not acceptable. For additional information, contact the National Oil Recyclers Association. Oily water is a problem for recyclers, so try to minimize the volume.

Please notice that most of these suggestions focus on safety. Cleaning out a fuel tank is no complicated trick with the proper tools. Doing so safely and efficiently requires thought and preparation.

If you are looking for effective fuel treatments that can prevent future contamination and system corrosion, we have a new eBook available online Marine Fuel Additives. Dealing with everything from ethanol gas treatments to diesel biocides, the book is the first of its kind to separate the true elixirs from the snake oil. 

Comments (12)

I might suggest placing two racors side by side with the ability to switch between them. Saves problems if you foul one with contaminants. I also have installed a polishing circuit with a March pump and a Racor 1000. Periodically I can polish the fuel and always before leaving on a trip polish the contents of the tank. It's been my experience that whenever faced with an engine problem, it's always the fuel!

Posted by: SailinRN | March 26, 2017 6:35 PM    Report this comment

I might suggest placing two racors side by side with the ability to switch between them. Saves problems if you foul one with contaminants. I also have installed a polishing circuit with a March pump and a Racor 1000. Periodically I can polish the fuel and always before leaving on a trip polish the contents of the tank. It's been my experience that whenever faced with an engine problem, it's always the fuel!

Posted by: SailinRN | March 26, 2017 6:34 PM    Report this comment

I might suggest placing two racors side by side with the ability to switch between them. Saves problems if you foul one with contaminants. I also have installed a polishing circuit with a March pump and a Racor 1000. Periodically I can polish the fuel and always before leaving on a trip polish the contents of the tank. It's been my experience that whenever faced with an engine problem, it's always the fuel!

Posted by: SailinRN | March 26, 2017 6:34 PM    Report this comment

In 2015, in preparation for sailing to Hawaii, I had my tanks (2 x 75 = 150 gals) cleaned, new cover gaskets installed, and fuel polished by a professional company that also services Microsoft's backup generators. The tanks were almost full and pressure washed with the fuel itself as it was being polished. Then the tanks were emptied one at a time and hand cleaned (found some plastic thingy in the starboard tank) before polished fuel was transferred back into the tank and measured so that I would know the exact capacity of each tank. This took them about 4-5 hours and cost me $1,415 including tax. That winter I install new primary and secondary fuel filters and added biocide.

We departed for Hawaii in 2016 and still felt it necessary to change the primary Racor filter in Hawaii before returning as the filter was very dirty with about 85 engine hours logged. That was a good decision as the return voyage to Washington required 88 more engine hours and we traversed some rather turbulent waters and a gale requiring to be hove-to for 30 hours off the coast. During the 2016 winterization both filters were changed again and the entire Racor assembly necessitated a thorough cleaning due to captured debris.

Even if the tanks have been cleaned you can't pay too much attention to your fuel filtering system.

~ ~ _/) ~ ~ MJH

Posted by: MJH | March 26, 2017 1:55 PM    Report this comment

Hi Guys, we took our boat around the world (Beneteau 440) over a ten year period. Ocasionally, we refuled at a dock but most of the time we refueled from two flex tanks and several jerry jugs. Always when we transferred fuel form the jugs or flex tanks we did it through a Baja Filter. As the Beneteau 440 has only a 50 gallon main tank, it follows that most of the fuel was filtered through the Baja. Many time we jerry jugged fuel from all sorts of unusual places: small suppliers' basement tanks to gas stations. Some of it filthy necessitating frequent cleaning of the Baja. Anyway. following the circumnav I had the tank desludged. I participated in the exercise at a full spectrum marina. There was really very little to remove which attests to the use of a Baja. Bake

Posted by: ARGONAUTA I | March 26, 2017 11:28 AM    Report this comment

I use Isopropanol (alcohol) to do the wipedown of the inside of the tanks. It is nonflamable and cheap.

Capt jim

Posted by: f136661 | March 26, 2017 9:46 AM    Report this comment

For those with smaller yachts and smallish fuel tanks the use of a BAJA filter will virtually eliminate contaminants BEFORE entering the fuel tank . Its use on larger tanks will require patience but you will be rewarded in the long run . Captain Dave Nicoll "Glory Days "

Posted by: Captain Dave Nicoll | March 26, 2017 8:37 AM    Report this comment

Had mine done for $200 in 2015.

s/v PassePort.

Posted by: Skipper | March 26, 2017 8:17 AM    Report this comment

Not sure if this "comment" will be checked 3 years after the article was published, but here goes...

I recently purchased a boat that had seen relatively calm sailing and motoring the past 5 years. After 170 miles of 7-12 ft swells in a 32 hour period, the engine decided to take a break. Jello was what I found in the primary filter. The metal tank is glassed into the boat and there's no access port. I don't think I have the resources to do or pay for a serious tank cleaning. I'm not sure to what extent the sludge that came out in the filter is still hanging around in the tank.

I was thinking a potentially effective way of monitoring "jello" build up in the fuel line, and preventing a clogged-filter failure would be to install a third (pre-) filter before the primary. I had in mind a clear bowl with 380 micron stainless steel mesh such as this (Goldenrod(R) Fuel Tank Filter from Do folks have any thoughts on the effectiveness of this, and considerations for installation and safety?


Posted by: rjm | October 27, 2015 2:14 PM    Report this comment

Setting the bio problem aside for a minute, is there anything a sailor can do to make sure the crap doesn't get into his tank to begin with? I just spent both legs of a trip to Block Island draining water and crap from my Racor fuel filters. As I don't trust the providers to do it, does anyone know of some kind of filtering setup you can put between the pump and your tank? I'd invest in something serious at this point. The problem is that bad. I just didn't know whether the velocity of the fuel being pumped would overwhelm a normal filter.


Posted by: RICK F | August 27, 2012 7:48 PM    Report this comment

I don't recall the specs on the MarPro oil extractor, but anyone considering using an oil extractor for this sort of work should check the continuous duty rating. Some are not rated to run for more than a few minutes without overheating . . . or worse. In any case, make sure the pump is protected by the recommended fuse. A manual pump will avoid over-current-related risks.

Posted by: Darrell | August 17, 2012 9:07 AM    Report this comment

Several months ago I bought a MarPro oil extractor. After the initial use I cleaned and stored it onboard. A few weeks ago I had to change the fuel filter, sure enough it was clogged. With a new filter and clean filter bowl I saw some particles as I pumped up the pressure to the diesel pump. I put the Marpro to work pulling diesel for the tank using the large hose till empty. Man all sorts of sediment was in the oil extractor enough that I decided to completely remove the tank, take it home and pressure wash it. Good thing it took several shoots with the pressure washer. I saved the diesel about 4 gallons, strained it, added Sea Foam and Bio Guard. Runs Great. The MarPro is simple and has pretty good volume. Be sure and take a bundle of baby diapers in case of an on board spill.

Posted by: Dove | August 15, 2012 2:22 PM    Report this comment

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