Condensation that didn’t happen before

Pablo Canales

Pablo Canales

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Pablo
I’ve owned a Cessna 205 for 4 years now, with Monarch Caps installed and never saw a drop of water in the fuel.


But since 3 weeks ago it doesn’t matter if it rains or not, every morning after the first flight, a significant amount of water drains out of the left tank.

I’ve replaced my Caps O-rings but still getting water every day.

How other way can humidity enter the tank, that it didn’t before?
 
Which tank do you refuel first? Maybe you're getting a slug of water in that tank when you start the refueling process.
 
are you seeing any visible moisture in your hangar?....on the floor or wings?
 
Pablo Canales said:
Can be the right or left tank, but same result :confused:
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Are you filling the tank all the way to full? If so, you're not getting condensation related water. There's no air in the tank to hold (and release) the condensation.
 
kyleb said:
Are you filling the tank all the way to full? If so, you're not getting condensation related water. There's no air in the tank to hold (and release) the condensation.
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Exactly! That’s whats making me go crazy! How is water getting in there if tanks are full and condensation is not possible.
Maybe somehow water is forming during flight?
 
tape a plastic bag over the fill cap when parking overnight....and see if it still happens.
 
Pablo Canales said:
Exactly! That’s whats making me go crazy! How is water getting in there if tanks are full and condensation is not possible.
Maybe somehow water is forming during flight?
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I'd put my money on water being introduced in the refueling process and not migrating to the fuel drains until the airplane is flown. The geometry of the tanks means the inclines aren't steep and there are obstacles in the way that could trap water until the aircraft gets some bumps, shakes, etc, from activity.
 
Tanks are vented. Condensation is common when temp and humidity conditions are right. That’s why we sump tanks.
 
My theory is you’re not getting all the water out after a single event. When you fly more makes it to the drain.
 
Salty said:
My theory is you’re not getting all the water out after a single event. When you fly more makes it to the drain.
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That's a reasonable guess. I'd still take a hard look at the refueling situation.
 
Most airport fuelling stations are not sumped every day. They should do daily water tests and sump the storage tanks daily. It should be logged somewhere.

Most simply hope the water never reaches the pickup tube level.
 
You have four options.

Bad fuel
Leaking Caps
Water not being fully removed during dumping.
Condensation.
 
pfarber said:
Most airport fuelling stations are not sumped every day. They should do daily water tests and sump the storage tanks daily. It should be logged somewhere.

Most simply hope the water never reaches the pickup tube level.
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We (FGU) sump them daily and keep logs of the findings and conditions. When I go to turn the valve on behind the tank, there’s a consistent slug of water that comes out each time. You’ll never get all of the water out of the tank, and you’ll waste a bunch of fuel even trying. In our AvGas tank, the pickup tube level is at the top, as I’d think most are and the majority of the water will be laying in the unusable area at the bottom. Still, the chance is always there, that’s why we try our best to sump our aircraft’s tanks after fueling and before each flight.
 
pfarber said:
Most airport fuelling stations are not sumped every day. They should do daily water tests and sump the storage tanks daily. It should be logged somewhere.
Click to expand...
Most don't need to go that far. Properly designed tanks don't take the fuel off the bottom of the tank; the pickup is above the bottom a bit to avoid sucking up debris (like rust) or water. Weekly is good. I looked after the fuelling tanks at our airport for 14 years, at least, in a fairly dry climate, and monthly sumping never got more than a cupful of water out of a 17,000-litre tank (4500 gallons), and some of that was rain or snow that blew sideways into the vent stack covers. The fuel pumps should have waterstop filters on them in any case; those filters have a silica gel media that traps water and will not let it pass. If the media becomes entirely saturated, all flow stops. The filter canisters had drains on their bottoms as well, easy to check frequently.

But seeing the rusty equipment at some FBOs, you have to wonder at the inside of their stuff. Waterstop filters aren't cheap, either, and maybe they're not using them. False economy, that, in comparison to the lawsuit that could arise from a contaminated fuel-caused crash.
 
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