T&T: Fuel Tank Design

[Bob Austin]

There are a number of variations of tanks which have drains at the low point.
The best I have owned came with a Sabb engine.  It was a 20 gallon cylinder SS
tank, with a bowl welded at the bottom.  At the top of the bowl was the fuel
petcock for the engine feed, and at the bottom of this bowl was a second
petcock for draining off the water and contaments.  I used this as a "day
tank" and it was very satisfactory.  The two main tanks drained from the
bottom of the tanks and did pass thru course filters on the way to filling the
day tank.

I have also owned several boats which had either draw tubes or petcocks at the
high end of the bottom of the tank, and a second petcock aft at the low end of
the tank to drain off the water and crud.  This also works quite well.

For our long range cruising boats, we would pump all of the fuel from one tank
thru filters to the second tank when both were over half down, every 6 months.
We would then open the man hole on the top or side of the tank, and use a
suction pump to remove the rest of the diesel or crud--thru filters to the
other tank or discard.  Finally we would clean the bottom of the tank with
paper towels and repeat for the second tank.  This assured us of always clean
fuel, since we used a Baja filter when filling the tanks.

So, there are a number of ways around the problem.

Bob Austin