well at least it wont go rusty . the same as mineyou was lucky keep poking you may get more as this is what i got from my compressor also pre-cleaned out
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just had a quick play and yes after a quick poke with a cable heared a glug and got about a teacup of water
have had a 2nd go at it got to 6cmf and releast the drain but only a little more coming out a very small amout
its a big tank so makes no odds if there's a gallon or so in it 





