Peter Dohm wrote:

According to annecdotes that I heard many years ago, service station gas
tanks have always contained some water--but since the gasolene is lighter,
the water settled to the bottom, so they were able to draw straight gasolene
from a floating pickup. According to those annecdotes, there could have
been as much as a couple of feet on water below the gasolene before it was
drawn of as part of periodic maintenance, with the result that the apparatus
were designed to shut off with a considerable level of liquid remaining in
the tanks--in order to avoid pumping water.

Speaking as someone who pumped gas to earn tuition money back in the
early 60s before there was gasahol, we'd 'stick' the tanks daily at
closing time to verify the amount in the tanks. There was always some
water that was evident at the bottom of the stick, but it was never more
than an inch or so.