"Roger Long" wrote in message
...
"Capt. JG" wrote

Water absorption in diesel? Seems to me that would be a very, very small
issue, given that they don't mix.

But they do. See Rich H post below.

If the bio is stuck to the sides, why would you want to knock it free?

So that it can get into the filters to be removed and not come off at an
inconvienient time. Biocide is just a way of assisting its removal but
the stuff is nasty and tends to dump a lot of stuff into your filter
system all at once if the tank is badly fouled. The mechanical action of
slack tanks gets some of it into the system more gradually; especially
with some assistance from something like StarTron.

Star Tron disperses the bacteria, but it doesn't do anything for a badly
fouled tank. If you're talking about a tank that's pretty good, maintained
with good fuel and you're careful about water egress, then the amount of
bacteria stuck to the sides would be minimal. In fact, they would die when
covered with fuel, and then they would pass naturally out of the tank. If
action is needed to get the bacteria out, I would much rather take that
action in a known timeframe vs. have it slowly clog a filter. If you're
going that route, then get a pressure gauge and put it on the filter. Then,
you'll know when the bacteria are starting to clog it. I can't imagine
wanting the sloshing action to break loose a bunch of decent size pieces and
have it immediately kill the engine.

If one has a badly fouled tank, that needs to be dealt with next to the
dock, not at sea.

Keeping the tank "topped up" to the extent practical in normal operation
usually means that there will be full air and water vapor access to the
entire surface of the fuel. The difference between that and a slack tank
is insignificant (for a nearly straight sided tank) and, as Rich points
out, more fuel volume for the same air/fuel contact area means more water
absorbtion.

I don't understand. If the tank if full, it's full. If you're using the
engine, you're using the engine, and when you get back and top it off with a
couple of gallons, it's full again, and whatever bacteria is alive for that
brief period when it's not full will quickly die and drop to the bottom. I
also don't understand the "absorption" issue with diesel. The diesel and
water don't mix, so whatever there is would be minimal to say the least and
it certainly won't hold bacteria.


--
"j" ganz @@
www.sailnow.com