BIOCIDES-Use or Don't Use

Rasselas36

Rasselas36

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Oct 4, 2008
147
Hunter 36 Mulberry Cove Marina
Recently I discovered a larger amount of algae in my fuel filter. After removing and cleaning, my close friend suggested maybe it time for me to introduce a biocide in my INCA poly fuel tank. When I read the articles and forums on using biocides I was left unconvinced. Practical Sailor had the best article and was the only site I found that actually tested biocides but still left me undecided. Perhaps one of you can help me make this decision.
 
Davidasailor26

Davidasailor26

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May 17, 2004
5,564
Beneteau Oceanis 37 Havre de Grace
Unfortunately if you're seeing algae in your filter it may be too late. Biocides can prevent algae growth and maybe kill what's there, but even dead algae will stay behind and clog filters.

We do add biocide (biobor) with each fueling. Figure it can't hurt. On our previous boat we didn't use it, and ended up with significant growth. Had to fish all of that out and have been using biocide since.
 
D

dlochner

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Jan 11, 2014
12,772
Sabre 362 113 Fair Haven, NY
The problem isn't algae. Algae is a plant and needs sunlight to grow, something missing in the fuel tank. The problem is bacteria and other micro-organisms. The common problem is lots of crud that fouls filters and fuel systems. However, there is a more serious issue that doesn't get mentioned very often.

There is a group of micro organisms that feed on sulfur that is present in diesel fuel (even low sulfur fuel) the byproduct of their life is sulfuric acid which gets trapped at the in the colony and will react with the aluminum causing it to corrode. Search the internet for Microbiologically Induced Corrosion (MIC). Here's a link to the Wikipedia entry: https://en.wikipedia.org/wiki/Microbial_corrosion

So the short answer to your question is yes use a biocide in your fuel tank. If I recall correctly, PS recommended Biobar.

@thinwater has considerable knowledge about the subject. Perhaps he'll weigh in.
 
Gunni

Gunni

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Mar 16, 2010
5,937
Beneteau 411 Oceanis Annapolis
The bio growth you are seeing lives in water that accumulates in your tank. Get the water out of your tank, it will be on the bottom, just above the sediment layer of dead biogrowth :oops:

As noted by DavidSailor you likely have an advanced situation that will require draining and cleaning out the tank to get the growth and sludge. Alternatively you could buy a case of filters and get used to changing them at the most inconvenient times. Going forward use Biobor JF and regularly (yearly) dip your tank to determine presence of bottom water. Get a new fuel cap gasket every year.
 
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Justin_NSA

Justin_NSA

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Jul 7, 2004
8,481
Hunter 30T Cheney, KS
+1 for BioBar. The PS article convinced me to do the preventive. I also use an H2Out dryer on the fuel vent to keep moisture from coming in that way. The desiccant crystals are reusable
 
thinwater

thinwater

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Mar 26, 2011
3,681
Corsair F-24 MK I Deale, MD
The short version is that biocides are one of a number of preventative steps. They absolutely work, but not alone. Keeping the fuel dry is critical. Turning it over helps. But once you have a significant fungal infection, the cure is a complete cleaning, because even if you kill the microorganism, you still need to haul the dead bodies out.

Typically when someone says "biocides don't work" it is one of these reasons:
  • They added biocides and then the clogging got worse. This is true. The bugs died, sloughed off the walls, and clogged the filters and lines. I've seen this happen many times. It can shut you down like a wall.
  • They believe that fuel polishing and keeping very clean fuel is a better approach. This school is at least 2/3 correct. IF the fuel is kept very clean and dry, even if infected, the extent will be so small it probably won't be troublesome or possibly even noticeable. No water, no growth.
I've experienced this numerous times on an industrial scale. If it were me, I'd pump the tank out, clean it (I'm sure it's due anyway--that is probably one of the contributing factors), and then refill with treated fuel to mop up the bugs I missed. Then I would take a close look at my filtration system and decide what upgrades it needs. Also check the fuel cap--and vent one of these is probably allowing water into the tank. Silica gel vent filters help. Using the engine more helps.
 
thinwater

thinwater

.
Mar 26, 2011
3,681
Corsair F-24 MK I Deale, MD
Rasselas36 said:
Recently I discovered a larger amount of algae in my fuel filter. After removing and cleaning, my close friend suggested maybe it time for me to introduce a biocide in my INCA poly fuel tank. When I read the articles and forums on using biocides I was left unconvinced. Practical Sailor had the best article and was the only site I found that actually tested biocides but still left me undecided. Perhaps one of you can help me make this decision.
Click to expand
What is the cause of your indecision?

It's not likely to get better on its own. Most likely it will get considerably worse unless you do something. Are you considering other options?

BTW, Yacht World did some testing years ago. Similar conclusions.
 
M

markwbird

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Nov 26, 2012
1,654
C&C 40-2 Berkeley
I always add a biocide additive when I fill up. I have never had problems with bacterial growth in the tank. Knock on wood.
 
Rasselas36

Rasselas36

.
Oct 4, 2008
147
Hunter 36 Mulberry Cove Marina
Just needed to hear from the crowd. Decision is will add biocide tomorrow. Thanks to all who contributed. Have a Happy and filling Thanksgiving and if any of you are VETS thank you for your service.
 
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NYSail

NYSail

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Jan 6, 2006
3,136
Beneteau 423 Mt. Sinai, NY
I go the opposite way..... I start with a clean tank then use my fuel. I never keep the tank full unless I’m leaving for a trip. I believe in using fuel so usually I’m below 1/4 tank. Winter I hope to have tank much less than a 1/4 tank. Have a racor 500 for water separation. I’ve had both aluminum and plastic fuel tanks. I guess it’s my climate and “luck”. I don’t add anything and have never had a problem. But many people add every full and also never have problems.....

Good luck
Greg
 
weinie

weinie

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Sep 6, 2010
1,297
Jeanneau 349 port washington, ny
I read the PS biobor article.
Without conclusive proof, its effectiveness is anecdotal.
I didn't use it this year...for the first time ever.
 
D

dlochner

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Jan 11, 2014
12,772
Sabre 362 113 Fair Haven, NY
weinie said:
I read the PS biobor article.
Without conclusive proof, its effectiveness is anecdotal.
I didn't use it this year...for the first time ever.
Click to expand
NYSail said:
I go the opposite way..... I start with a clean tank then use my fuel. I never keep the tank full unless I’m leaving for a trip. I believe in using fuel so usually I’m below 1/4 tank. Winter I hope to have tank much less than a 1/4 tank. Have a racor 500 for water separation. I’ve had both aluminum and plastic fuel tanks. I guess it’s my climate and “luck”. I don’t add anything and have never had a problem. But many people add every full and also never have problems.....
Click to expand
You guys must love living dangerously! :poke:

I'm not certain what you would call "conclusive proof."

We know that:

Microbes can live in the interface of water and diesel fuel. That's a lot of black crud you get in the tank.
Microbes live and die and leave their little bodies to accumulate as a sludge.
Some microbes produce very acidic waste products, think microbe pee.
Aluminum reacts poorly to acid.
Pick up tubes in fuel tanks do not reach the bottom of the tank, so by the time they pick up the sludge, there is a lot of it.
The aviation industry is very concerned about microbes in jet fuel. Jet fuel and diesel are not chemically that different.
Murphy says that the filter will not clog with dead microbes when the boat is safely at the dock.
Water gets into the fuel tank in various ways, sometimes through the tank vent, sometimes through failed filler gaskets.
Water is heavier than diesel so it settles to the bottom of the tank where it is not evacuated by the fuel pump until there is way too much water.

I think those are enough reasons to keep a fuel tank full and to use a biocide. However, your boat, your life, just think of the folks who would have to effect a rescue as your fuel filter clogs on a lee shore.

Using an additive is cheap insurance.
 
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thinwater

thinwater

.
Mar 26, 2011
3,681
Corsair F-24 MK I Deale, MD
weinie said:
I read the PS biobor article.
Without conclusive proof, its effectiveness is anecdotal.
I didn't use it this year...for the first time ever.
Click to expand
The biocides absolutely kill the bugs, both in the lab and in the field. This has been measured and there is no question on this point. There is no question that they can prevent significant growth in a tank. This has been proven over and over and over again in testing by many parties.

That is not to say you must use them, that there are not other ways to keep a clean system, or that they will clean a system that is dirty. But to state the effectiveness of biocides is anecdotal is to misunderstand the word.

an·ec·do·tal/ˌanəkˈdōdl/
adjective
adjective: anecdotal
(of an account) not necessarily true or reliable, because based on personal accounts rather than facts or research.
 
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