(a) You can go through the math all day long and still not explain why I
have drained the (hangared) 182 after a particularly humid day or two and
get a tablespoon or two of water in the quick drains

I had the same problem after annual once. I called the A&P back and he
readjusted the cap. 5 years later, sitting outside, with never more
than 1/2 tanks, I haven't gotten even a drop of water in the tanks.

-Robert