Metal vs. Plastic Fuel Tanks

[thinwater]

I read a lot of threads about corroded tanks.


There seems to be significant research that copper, zinc, lead, and their alloys (terne, solder, and brass) adversely affect diesel stability. Samples kept in glass last for many years, but add a few hundred ppm water, a few ppm salt, and any of these metals, and the fuel may last only months. Additionally, all of the major diesel engine manufactures and ASTM basically ban copper and galvanized from tank installations. Several caution against terne. carbon steel, aluminum and stainless are not implicated, but each has its own problems.


Most cars (more than 80% of US market) use plastic tanks, with the only large exception being aluminum tanks on large trucks.


My last two boats had plastic tanks. No problems. And both were designed so that I could have removed and replaced the tanks in an hour, but that is a different issue (but the water and waste tanks would have required a saw and glass work--go figure).



So are metal tanks and copper lines an anachronism? Has anyone had trouble with plastic tanks? I haven't heard of any. Sailing has a lot of tradition. We are a conservative lot.

[David M]

HDPE is an excellent material given it does not corrode. Just make sure you get a wall thickness that you believe to be sufficient. You can have HDPE tanks custom made to your dimensions and wall thicknesses.

[thinwater]

Originally Posted by David M

HDPE is an excellent material given it does not corrode. Just make sure you get a wall thickness that you believe to be sufficient. You can have HDPE tanks custom made to your dimensions and wall thicknesses.

Gasoline tanks must be built to code, but diesel not required. PE is also available in low-permeation versions. Companies like Moeller make a LOT of sizes.

[kmacdonald]

The only problem I have with plastic tanks is the fittings. They tend to be harder to seal and not as strong as aluminum. They also give off an odor. Not sure if it's the fuel inside or the plastic itself.

[thinwater]

Originally Posted by kmacdonald

The only problem I have with plastic tanks is the fittings. They tend to be harder to seal and not as strong as aluminum. They also give off an odor. Not sure if it's the fuel inside or the plastic itself.

What is the age of the tank? There were major regulatory and design changes in ~ 2012. Unlike the CARB jerry cans, these were actually big improvements!

[kmacdonald]

Originally Posted by thinwater

What is the age of the tank? There were major regulatory and design changes in ~ 2012. Unlike the CARB jerry cans, these were actually big improvements!

Not sure of the tanks age but was purchased maybe four years ago. What were the changes?

[thinwater]

Originally Posted by kmacdonald

Not sure of the tanks age but was purchased maybe four years ago. What were the changes?

Lower permeation is the main thing related to tanks, which in many cases also increased wall thickness. Also lower permeation hoses and improved venting (emissions control, and by extension, less water absorbed into the gasoline and less gasoline loss).


Is it an installed tank or a portable tank?

[kmacdonald]

Originally Posted by thinwater

Lower permeation is the main thing related to tanks, which in many cases also increased wall thickness. Also lower permeation hoses and improved venting (emissions control, and by extension, less water absorbed into the gasoline and less gasoline loss).


Is it an installed tank or a portable tank?

It's an installed tank and was sold as such. Below deck tank I think is what it was called.

[FlyingScot]

As someone who recently replaced two aluminum tanks with polypropylene, I'll stick with the plastic. Both 10 year old tanks were weeping. One more than the other, especially when full.

Being able to see through the tank walls is a bonus.

[thinwater]

Originally Posted by kmacdonald

It's an installed tank and was sold as such. Below deck tank I think is what it was called.

Brand and size? Sorry for all the questions.

[kmacdonald]

It was a 12 gallon tank for the Capri 22. Not sure of the brand. There is a distinct odor it gives off.

[sailcrazy]

We replaced our black iron diesel fuel tank with a 10mm thick Hi Density Polypropalyne tank about 7 years ago. It was custom made forus by a shop in Marmaris, Turkey, and aside from the screw-in fittings not sealing real well (until I applied some proper dope to them) we've had '0' issues with them. Highly recommend for my money!

[groundtackle]

Originally Posted by kmacdonald

It was a 12 gallon tank for the Capri 22. Not sure of the brand. There is a distinct odor it gives off.

I agree, they stink. Even well built heavy wall custom have the issue over time.
As safe as they are I hate that smell. Aluminum is the same, takes a few more years though.
Chris

[oleman]

I see the plastic tank as a fire hazard but also the entire plastic boat also.

The day a major country builds a warship from plastic I will come onboard.
My choice of material in 2019 is monel.

[roverhi]

Having almost everything made from plastic essentially self destruct from UV, age or just orneriness after not very many years not sure I'm convinced plastic is for the long haul. Diesel in Aluminum and SS tanks seems to work just fine for years. The fuel in the Pearson 35's aluminum tank is going on 6 years and engine ran fine for a few hours just last week.

I can see advantages for plastic tanks that are exposed to moisture like in the bilge but wouldn't scrap a metal tank just because I was worried about fuel contamination from the metal.