Diesel Fuel Tanks

I got this interesting letter from Peter Eikenberry, an ex-US Coast Guard guy working with vessel standards. He points out that my perception that all fuel tanks had to exhaust (drain) from the top did NOT apply to diesel! This is good news because since fuel floats on top of water, all the old time tanks had a "bulb" like a pint dish pan welded to the bottom, and the fuel line would exit from the top of the bulb and there would be a petcock drain on the bottom of the bulb. You would open this drain and let a little fuel flow out into a cup before starting the engine. That would remove any water (from condensation or bad fuel). Very simple, but rarely seen today. As I said, I thought it was illegal so am glad to hear it still IS legal for diesel!

   Here's a 30 year old "old time" diesel fuel tank, formerly on a Saab engine, later used for a diesel heater in a shop. Note the fuel "bowl" has a water drain on the very bottom and the fuel line is at the top of the bowl.

Anyway. Just one comment relative to both books. In both you made a statement about diesel fuel tanks, claiming that the Coast Guard does not allow drains or openings below the top of the tank. This is true of gasoline powered recreational boats, but not true of diesel powered recreational boats.

I was an engineer in the Coast Guard Office of Boating Safety for many years and over time became the CG representative on the ABYC fuel systems committee, also on the SAE Marine Fuel System committee, and was generally the go to guy on fuel systems in our office. The fuel system regulations that apply to recreational boats apply only to gasoline powered boats. Diesel fuel systems are not regulated by the Coast Guard for recreational boats. They are, for commercial vessels, unless it is a six pack (six or less passengers for hire) boat, which is a simply a recreational boat.

ABYC does have a fuel system standard for Diesel fuel systems but I have read through the standard (H-33 Diesel Fuel Systems) and can find no prohibition of drains, in fact there are specifications for the valves used in fuel tank drains on diesel tanks.

This is a common misconception and I have taken literally thousands of phone calls and written inquiries over the years concerning diesel fuel systems. How this all started is before my time but it is one of those popular myths that just seem to grow on their own steam.

Peter D. Eikenberry Sr.

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