Suggestions for a diesel day tank.

[GILow]

I finally tracked another mystery diesel leak on the boat to the 50 litre SS gravity feed tank above the engine. Looks like the tank is starting to fail at the seems. It's 30 years old, so I reckon it is for the bin.

A replacement SS Cruise tank of similar dimensions is a fairly brutal AU$400 without a fuel gauge, and then the tank will need some mods as it only has one breather and a pickup, whereas I need a breather, a pickup and a return line. I've been living with an arrangement where I "T"d the return line to the breather, but it's a pain when filling as it takes the filler a moment to "burp" the breather line clear before the tank fills smoothly. Usually end up sloshing a bit of fuel out the filler port.

The location of the tank is pretty easy to get at, it just slides into a shelf above the engine room. Current tank is a bit under 700mm wide, 500 mm front to back and about 200mm deep, 50 useable litres. There's a fair bit of room around the tank it all directions, so I can play with those dimensions a bit. The engine is a bit thirsty at 1 litre per nautical mile, so I'd like to have at least 50 litres in the new tank if I can. Transfer to the tank from the main tanks is done using a small electric diesel transfer pump or filling straight from a jerry can.

Can anyone suggest a more economical tank supplier or a clever way of throwing slightly less money at the problem? I've done the usual web searching but aside from somewhat suspect poly tanks, I've not found anything particularly budget friendly. Clearly it will help if the supplier is in Oz, but a supplier who will ship to Oz is also fine, I am no particular rush, I can use Jerry cans for now.

Are poly tanks OK to use in this situation...?

Matt

[GILow]

Hmmm... one suggestion just made to me is to just fibreglass the outside of the existing tank. Seems like it might be practical. It is only ever going to hold diesel, and it seems structurally sound aside from the failed seams. I am getting ok at fibreglassing, and it's a pretty straightforward shape.

A smart option...?

[boden36]

For vintage vehicle tanks there is a preparation that you wash around the inside of the tank to seal it. You buy it as a kit. Maybe it would work for diesel. Worth checking.

Regards,
Richard.

[Wotname]

Why are the poly tanks suspect that you have seen?
The "right" poly tank is suitable for diesel / petrol - reference plastic fuel containers and outboard tanks.

Another option is to build your own out of plywood and epoxy inside (and out).

[CptLawrence]

A fuel bladder can be put in the tank, might have to remove a baffle or imperfections that would puncture or wear on it. Rig a jerry can if in a pinch.

[DumnMad]

If its only the seams that are suspect maybe its repairable.

Its ss and with a bit of residual stress around the welds or bends the weakness may be very local.
Away from the stress points it may be very sound.

[GILow]

Thanks guys, a few very good suggestions for me to follow up there.

Matt

[Coxswain]

Mate, $400 is not too bad for something that will last you another 30 years...
Check around some of the wreckers yards, you may pick up an old tank there that just needs a cleanout?
You wouldnt be able to ship anything half decent from anywhere for less than $400.

[GILow]

Originally Posted by Wotname

Why are the poly tanks suspect that you have seen?

Sort of flimsy looking in the photos, and the threaded sockets for the various fittings look to be made of a separate material, making me worry that they will start to leak themselves. Might be paranoid, but that's the difficultly shopping on the web, hard to get a sense of the quality sometimes. At least with the $400 SS tank I could pick one up and have a good inspection, got to say I was not impressed though.

M

[GILow]

Originally Posted by CptLawrence

A fuel bladder can be put in the tank, might have to remove a baffle or imperfections that would puncture or wear on it. Rig a jerry can if in a pinch.

Yes, using the jerry for now, but I don't think I'd like to go open water with the current arrangement.

Had some nasty experiences with bladder tanks, has put me off them, might be silly of me, but I would never relax about it.

Matt

[GILow]

Originally Posted by DumnMad

If its only the seams that are suspect maybe its repairable.
.

Yep, checking out Boden36's suggestion now. Looks to be some decent sealants I can pour into the tank. They are cheap so I reckon they are worth trying first. Luckily the tank is very easy to remove and refit.

I think the construction of the tank is such that any attempt to reweld or braize the leaking area would just cause the next section to start leaking, so a liquid sealant will be more likely to work.

M

[neptunesjester]

I used poly tanks for my daytanks without issue. The wall thickness even allows for tapping in your own fittings, which I did for the transfer pump line between primary storage and the day tanks. The only time I had a preinstalled tap fail on a poly tank where the weld around the plug holdining the tap failed was on my holding tank where there was stress applied to the fitting by having too tight a bend in the sanitation hose. Won't make that mistake again.

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[sailing mike]

Why not have the tank re welded? It is no problem to Tig weld a s/s tank which has held diesel in it. Providing the welder knows what he is about. I have re-welded many tanks large and small....

Best regards

Mike on the sailing vessel Captain O'Brien


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[zeehag]

repair what you have as replacements all suck.
ask me how i know.
do not use poly tank as isnt the optimal size and shape for hold and will cause troubles. ask me how i know that one also...lol
fix what you have. i wish the po had done that with this boat.

[nimblemotors]

What issue did you have with bladder tanks, as I plan to use them.

Originally Posted by GILow

Yes, using the jerry for now, but I don't think I'd like to go open water with the current arrangement.

Had some nasty experiences with bladder tanks, has put me off them, might be silly of me, but I would never relax about it.

Matt