Can standing water penetrate a metal fuel tank?

[eddystone]

About to relaunch in next week or less and had a worrying thought. Owing to stupidity back in February I blocked a cockpit drain sea cock where I had removed the barrel but not finished the job. As a result the cockpit locker and empty engine bilge flooded and the bottom of the fuel tank must have been sitting in water for several weeks. (Believe it or not this happened twice as I blamed the accumulation of snow getting past the seals on the locker lid before I realised what I'd done!)
There was no trace of diesel in the bilge water and no previous evidence of a leak in what I presume is original S/S tank but is it possible to have pin prick corrosion holes that allow water to penetrate up into the fuel but not allow fuel to escape?

 

[RichardS]

Not possible. The fuel will always escape in the circumstances described.

Richard

 

[coopec]

I could be wrong but I think I have read that diesel will find pin-holes where water will not. I just did a search and of course your not Robinson Crusoe. Have you tried pressurizing the tank?

https://www.google.com/search?clien....2530...0i22i30k1j33i22i29i30k1.0.rgJnnFR-HAI

 

[PaulRainbow]

Not possible. The fuel will always escape in the circumstances described.

Richard

+1 :encouragement:

 

[eddystone]

That's re-assuring. One of the pleasures of this forum is the ability to check things anonymously rather than share my concern with the boatyard who would no doubt then regard me as terminally insane and add a "0" to the bills. I'm not saying I'm not actually terminally insane you understand, but perceptions matter. It's the product of a fertile imagination but no scientific training.

 

[PuffTheMagicDragon]

Irrespective of the relative densities of the two fluids, the diesel in the tank will have a higher head than the water that is outside if this is just touching the bottom of the tank. If there are pinholes in the bottom, the diesel will go out and no water will come in - unless the surface of the water is higher than that of the diesel inside the tank.
What you can do is to wipe all of the water that is below the tank and then spread paper napkins under the tank to indicate any leaks. The best colour for the napkins is blue because any drips will show up much darker, almost black.