I’ve owned a Cessna 205 for 4 years now, with Monarch Caps installed on it 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 the same.

How other way can humidity be entering the tank, that it didn’t before?

Hi! I currently own a Cessna 205 with Monarch tank caps installed on it.

Water has been appearing in my left tank right after I land this past 2 weeks.
Always after I fly, never in the morning.

I’ve had this plane for a couple years now, and I’ve never seen water before. But lately water shows up right after each flight.

On my first flight of the day, I drain my tanks and they all come out clean.

I assume water is somehow hiding inside my tank, and after the first flight it runs to the drain area of the tank?

We already changed the fuel cap O-Ring

The real question is (how is water getting into my tank?

It never did before
And It has not rained lately

Check fuel cells for wrinkles, especially near the sump.

What he ^^ said. All that water has likely been in there for a while, and just gradually working it’s way to sump.

Try a really, really enthusiastic “shake, rattle and roll”. Then check sumps again.

MTV

I flew C205's for many years and it isn't unusual for the bladders to have some wrinkles that can hold quite a bit of water. Climbing, descending and even cruise can shake the water around and that may be what is happening.

I was one of the planes that caused the FAA to create an AD for a drain on the fuel boost overflow tanks under the floor boards of the Pilot & Co Pilot seats.

I experienced an engine failure and the cause was a lot of water had settled in those small tanks, which are the lowest point in the fuel system. Go figure how that happened.

Do you have the quick drains on the overflow tanks?

Do you push up & down on the wings as part of your pre-flight before draining fuel?

Feel free to make contact if you have any question.

Rich

Might be the source? Water can hide in fuel being transported.

8GCBC wrote:Might be the source? Water can hide in fuel being transported.

What he said ^^^ if you know it’s not been exposed, it got in there somehow..

If it's always only on the left side, that would seem to speak against a contaminated source.

How humid is it where you fly? How much does the temperature swing? Are you hangared? It could be condensation in your fuel tanks from big temperature swings in humid climates. If your tanks aren't full, it could be condensed on the roof of the bladders, and sloshes into the fuel during flight. You might try the vigorous wing shake followed by letting it sit for 10 minutes, then sump.

I've got Atlee Dodge cap adapters on my 205. As far as I can tell they don't leak. I have noticed a little bit of water (similar to your picture) when I camp someplace humid with the airplane out in the open (vs hangared). If you have dew on the plane, you likely have dew in the plane...