Fuel tank plumbing

Just installed two new 170 gal aluminum fuel tanks in my single screw trawler and getting ready to install the new fuel lines.
I was planning on pulling fuel up the pickup tube and out the top of the tank to the fuel switching valve but just read an article by Tony Athens the Cummins guru and he recommends putting a T in the fuel balance tube at the bottom that connects the two tanks instead of using the fuel pickup tube. Just curious how others have theirs plumbed?

I'm a "bottom feeder".

My fuel comes out of the bottom of the tank, from a sump at the lowest spot.

Plumbed it this way 19 years ago and have had no issues.

I can run the tanks down to less than 2 gallons and pump any water or contaminent out with the built in pump if present. I've actually never had water in my tank.

Make sure you have a good shut off valve at the outlet fitting.

I draw from the top and use the bottom drains for fuel polishing and transfer. My charter boat has one tank that i designed with about a one pint sump. The fuel pickup goes in the top down to the bottom of the sump. While I like this design, you must be diligent in checking the fuel separator as any water or contaminants will quickly end up in the sump and then the separator. My separator is oversized (Racor 1000) to handle this quick loading of water or contaminants.

Ted

I recommend a bottom feed if much of your machinery is below the tops of your fuel tanks.


While it encourages leaks if there are any, after living with air leaks, I prefer cleaning up a weep over the engine shutting down unexpectedly from an air leak.

Mine also uses a bottom feed. It is also the balance hose. I don't have a dedicated sump though.

Like OC Diver and psneeld after refueling it is not long untill I check the filter drain to see if there was any water/dirt in the new fuel and I need to be mindfull of weeps.

I have good quality fittings, ball valves and hoses.

Propnut said:

Just installed two new 170 gal aluminum fuel tanks in my single screw trawler and getting ready to install the new fuel lines.
I was planning on pulling fuel up the pickup tube and out the top of the tank to the fuel switching valve but just read an article by Tony Athens the Cummins guru and he recommends putting a T in the fuel balance tube at the bottom that connects the two tanks instead of using the fuel pickup tube. Just curious how others have theirs plumbed?

Click to expand...

Tony’s rationale is that debris should not be allowed to remain in the tanks, but should be captured by the filtration system.
This is sound rationale, IF you have adequate filtration, so keep reading Tony’s Tips re proper filtration.
I would valve the tanks independently, regardless.

Propnut said:

he recommends putting a T in the fuel balance tube at the bottom that connects the two tanks instead of using the fuel pickup tube. Just curious how others have theirs plumbed?

Click to expand...

Thats what I did. I installed three tees in the fuel balance tube. One goes to the engine, one goes to a sight glass. There is also a tee in the lowest point to drain off any potential water.

Any boat with a bottom fuel connection might take a tip from the USCG

On over 6 pack sized boats a cable operated valve is used to be able to stop fuel in case of a fire.
The pull cable is operated from outside.
AS it is usually only on inspected vessels it might work to make the boat harder to steal.

My experience is big boats and ships. They're all pumped from the bottom. It makes changing your primary filters easier and sometime the secondary, too. As others said, you don't get air in the lines and there should be no tank debris the filter can't handle. Also you never have the pickup tube clog problem because the tank supply is usually bigger pipe than the fuel lines. And I have a cable pull shutoff on my fuel supply.
Having seen a lot of WWII boats that originally had big gas engines, I think the top down pickup tube came from the days of gasoline and got carried over to small diesel boats.