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timebandit 05-12-2009 02:45 PM

How come?
It seems that most fuel problems are caused by water contamination that allows thing to grow.:mad:

Gasoline problems seem to be caused by evaporation of the good stuff and water.:mad:


How come there is not a fuel tank vent line shut off with a pressure/vac relief valve and/or a water separator in the line?

I have a water separator on my compressor to protect my air tools from water and a orange plastic ball that screws to my paint gun to to prevent contamination if I paint.

JT1019 05-12-2009 02:49 PM

Why does someone always have to interject logic into the conversation? I think I need a beer….

tommays 05-12-2009 03:28 PM

The tanks BOTH gas and diesel have to meet CG regs for a TON of stuff :) and there NOT real open to changing what took a long time to make safe from what they learned from various boating accidents (FIRES)

Most square tanks cant even take 4 PSI or much vacume without having a stroke :)

eolon 05-12-2009 04:03 PM

Yeah, that's a good question. Federal VOC regulations require that all modern gas tanks be under moderate pressure. Excess pressure is vented through a canister filled with activated charcoal, which does a great job of absorbing the volatile organic compounds. When "make up" air passes back through the canister, the VOCs return to the tank. In this way the canister has a long life of absorbing and desorbing VOCs. Water vapor isn't much slowed down by the charcoal, so it can go into the fuel tank also.

During re-fueling, warm moist air has a great opportunity to enter the tank and condense into the cooler fuel. At this point, only a water separator (density separator) will remove the water, unless you add some ethanol to absorb it, but, of course, ethanol has its own problems...

Car manufacturers learned a while ago that it is better this way than trying to put a self-regenerating water absorber in the fuel line.

The one in your compressor is either amorphous silica or a refrigerated heat exchanger/condenser. Once it is saturated with moisture it stops working. Silica gel has to be regenerated by exposing it to high temperatures to dry it out again (silica gels usually have an indicator dye which tells the consumer when it is time to regenerate). The condenser has to be purged of water every once in a while, usually with a trap solenoid on a timer.

Neither of these will work well on a automobile or marine application, because of the regeneration step. With silica gel, regeneration would mean high heat through fuel lines (!) and a condenser would be an energy hog.

So, until someone invents a perfectly efficient, self-regenerating, cheap desiccant system, I think we are stuck with water separators and absorbers.

Best Regards,



timebandit 05-12-2009 11:19 PM

I use something like this.


It is metal so it would hold up better than the rubber vent hose.

It has a small drain screw to remove the water.

People change fuel and oil filters on a regular basis and I haven't had to change this filter for a couple of years, just keep on draining it.

I think I move more air through my air tools in a week than a fuel tank does in a year.

Omatako 05-13-2009 02:30 AM

I use a Racor filter which has a water seperator with a drain tap to drain water (so do most other boat owners) and a litre of fuel treatment in the tank every now and again.

I don't understand the problem.

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