Diesel tank dip tube question

[5akman]

Just returned from AK where I spent Easter week tearing up the back deck on my gillnetter to replace the leaky ply/glass tanks with aluminum. The shop and I mis communicated regarding the dip tube install and it didn't get done. I have 1" threaded coupler welded to the top of the tank and now need to build a dip tube. Any thoughts on what to use for material and how to construct it? I'm thinking of an alum or stainless bushing purchased from McMaster Carr, necking the 1" down to 1/2" but what do I want to use for the actual tube material? Alum? Rubber hose? Help!

 

[steveinak]

I think i'd use something rigid like aluminum tubing/pipe. Did Mike's Welding build you those thanks ??? I'd also have some type of inspection opening with a gasketed cover on the top of the tank in case you need to see inside it. Make sure to look inside it before you install it in case they forgot to take out a rag or some other junk out of the tank that could cause you lots of headaches down the road with clogging problems. Don't forget another nipple or port on the tank for the hose to supply the diesel stove/heater with fuel(very important !!)

 

[5akman]

I had Kenai Welding make them and paid to have a few extra baffles put in. It ended up being 3200.00 for the two 3/16", 166 gal tanks where Metal Magic quoted 4900.00. I do have two 1" threaded fittings on top for dip tubes, returns etc.

 

[Sailorgp]

If I were you I'd talk to the tank fabricator (or other tank builders) and see what they suggest.
What I've seen on the boats I've owned is an elbow that would screw into the 1" thread with barbs on both ends of the ell. The dip tube itself is a stiff plastic tube that fits over the barb going down into the tank. The other barb would accept the A2 rated fuel line.

 

[PaulR]

Stainless pipe, not tubing, TIG welded to a one inch bushing.

 

[Brooksie]

5akman, We just had a huge discussion on another forum about dip tubes vs: draw valves on the bottom of the tanks. Most, including myself, having two boats set up that way, agreed that drawing from the bottom of the tank put the water and sludge in the prefilters rather than forming a mat on the tank bottom requiring periodic "mucking out".

Have you considered that arrangement?

 

[Crabman]

While I like drawing from the bottom, there are precautions you have to take such as draining the tank into your bilge. Also, from the drawing above. I had a system like this on my longliner. Down stream of the Tee there is a loop/bend in the fuel hose. I had it just like this on my fuel system. It drove us nuts when sediment settled into the loop to restrict the fuel enough so that the engine would run rough but not enough to notice the clogging.

It clogged twice. The second time, we looked like we knew what we were doing and fixed it quickly.

 

[Brooksie]

So maybe like this, better

 

[5akman]

Hmm, interesting ideas. I do have a 1 1/2" "balance tube" port at the fwd bottom corner of each tank that I guess I could use for the supply location. I'll have to give this some thought!

 

[PaulR]

To mitigate sludge and clogs in the line, in the last series of drawings, have the lines from each tank flow into a one gallon tank, with large diameter drain fitting, ball valve, and plug or cap for safety. draw fuel for engine from midway up the settlement tank.

 

[Brooksie]

To mitigate sludge and clogs in the line, in the last series of drawings, have the lines from each tank flow into a one gallon tank, with large diameter drain fitting, ball valve, and plug or cap for safety. draw fuel for engine from midway up the settlement tank.

Good idea too, like a "day tank" but smaller & w/o all the valves an sight gauge. The dripleg coming out the bottom of the cross (in the drawing) can be extended as long as needed to hold more as long as you can get a can under it to drain the gunk/water.