Fuel Tanks - Stainless vs Plastic

[Enoch Powell]

Hi all,

A friend has told me that I should switch my stainless steel tank for a plastic one because you don't need to worry about diesel bug in plastic tanks. Is he right, and would you recommend doing this?

[Orion Jim]

The “bug” is in the diesel, not in the material the tank has been constructed of.

[ItDepends]

Originally Posted by Enoch Powell

Hi all,

A friend has told me that I should switch my stainless steel tank for a plastic one because you don't need to worry about diesel bug in plastic tanks. Is he right, and would you recommend doing this?

You need new friends who know something about boats, or maybe ones not trying to sell you plastic tanks.

“Bug” in diesel is microbial growth at the interface between diesel and water sitting in the bottom of the the tank. It has NOTHING to do with the material of construction of the tank. Get rid of the water, and no more “bug”.

You could make an argument that the metal tank would swing temperature faster because of its higher thermal conductivity, and that would lead to more condensation, and more water, and then more “bug.” You could make that argument, and even have a tiny bit of technical support for it, but in the real world it would not matter a bit.

[ChrisJHC]

Also, be aware that some safety audits (if required) expect metal fuel tanks.

E.g. in Australia: “Diesel fuel tanks shall be metal or other material certified as suitable by the manufacturer.”

[jordanbigel]

Shouldn't the question be Stainless, Plastic or Aluminum? Because I think the correct answer is Aluminum. No?

Stainless for water, Alum for diesel, plastic for waste.

[GILow]

Originally Posted by ChrisJHC

Also, be aware that some safety audits (if required) expect metal fuel tanks.

E.g. in Australia: “Diesel fuel tanks shall be metal or other material certified as suitable by the manufacturer.”

I don’t think you are really interpreting that accurately.

“Metal OR other material certified as suitable by the manufacturer.”

The key word is OR. There are plenty of plastic tanks certified by their manufacturer for diesel.

[GILow]

Originally Posted by jordanbigel

Shouldn't the question be Stainless, Plastic or Aluminum? Because I think the correct answer is Aluminum. No?

Stainless for water, Alum for diesel, plastic for waste.

Depends on which country you are in and which particular regulations apply to your situation.

Certainly that list is not one I’d follow.

[MikeHoncho]

My aluminum diesel tank failed. Plastic would not have

[Bowdrie]

Stainless tanks got a bad rap for a long time.
In the earlier days many were made from inferior grades of metal and the protocols of welding techniques weren't well established, (proper filler rods and gas usage,) as a result, over time many developed leakages at the welds.
If any water was present in the tank, the Sulphur in the fuel would react, creating acid which attacked the welds.
For fuel they need to be welded not only using TIG with gas surrounding the weld area, but they need gas on both sides of the weld.
With proper construction a stainless diesel tank can give very long service.
Aluminum can make an excellent tank, no doubt about that.
Can you keep salt water off of it? If not, there will be issues.
Can you drain it down to the last tablespoon? No matter the material any fuel tank should be so configured and have a valve with an attached hose that can be tie-rapped up out of the way, its end above the tank.
Every now and then stick the hose in a bucket and drain out some fuel.
For a fuel tank, if cost is not an issue, a Monel tank is superior to either aluminum or stainless.
A plastic tank? No thank you, at least not any that I've ever seen.
A previous post mentioned water tanks, stainless makes great tanks, copper makes them better.
You will have healthier water even just using copper piping for the water lines.

[ChrisJHC]

Originally Posted by GILow

I don’t think you are really interpreting that accurately.

“Metal OR other material certified as suitable by the manufacturer.”

The key word is OR. There are plenty of plastic tanks certified by their manufacturer for diesel.

Yeah, but then you have to be able to produce the certificate from the manufacturer which isn’t always easy.

Just finished prepping 2 x boats for the Sydney to Gold Coast so I’m well aware of how tricky it can be if you’re slightly off script.

[Enoch Powell]

Thanks for the help everyone. I had hoped that a plastic tank would prevent this. I have not suffered from this issue yet, I'm just paranoid. I guess I'll stick with my stainless tank and keep adding the biocide gear.

[goboatingnow]

Plastic seamless tanks are best for all liquids in my experience , anything with a welded seam can fail.