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post #1 of 27 Old 05-19-2013 Thread Starter
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Fuel tank drain

My ages-old 15-gallon stainless fuel tank is installed underneath one of the cockpit seats and is great in all respects other than not having a low-point drain to remove water/condensation build-up over time - even the pick-up tube comes out of the top! The only other downside is that it's fixed neatly under there in such a PITA-to-get-at way I can't even take a decent photo of it - but I can get at the underside easily enough.

I'm guessing that the tank is fairly thin-walled - certainly too thin to tap a thread. The only access to the inside is via the 1-1/2" fill tube.
  1. Can anyone recommend a smallish low-point drain/tap fitting that could be installed with the tank in situ?
  2. Could I get away with simply emptying the tank, drilling a hole and installing some kind of skin fitting in place? Will this seal properly?
  3. Is this even possible to do in situ or would I really have to get the tank out and have something brazed on? Can you braze onto stainless? Is drilling into the bottom of a tank even a good idea?
  4. If not, any better ways to fit a low-point drain??
Thanks,
Cameron

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"Honestly, I don't know why seamen persist in getting wrecked in some of the outlandish places they do, when they can do it in a nice place like Fiji." -- John Caldwell, "Desperate Voyage"

Last edited by Classic30; 05-19-2013 at 10:27 PM.
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post #2 of 27 Old 05-19-2013
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Re: Fuel tank drain

Not sure about regs Down Under, but in the US, a drain on the bottom of a fuel tank is not permitted. Here's the USCG requirements.

http://www.uscgboating.org/regulatio...rds_partd.aspx
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post #3 of 27 Old 05-19-2013
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Re: Fuel tank drain

Hartley,

You asked a question and i have had experience along the lines of your inquiry. Thanks for your input on my prop qusetion. Well first off i'll explain a little about myself, I'm not very popular on this site because of past posts involving a sensetive issue. That said I do all the maintance and repairs on my boat, a 2007 Tartan 3700, myself.

Ok, so here goes, you want to clean your fuel tank and there is no drain. I did this exact thing last year.Here's the thing, just open it up the through an inspection port and pump it out and do it. I agonized over it for some time but in the end it wasn't that bad. First thing go out and buy yourself the one of those Jabsco oil extraction units that run on 12 volts. You always wanted one anyway for end of season decommisioning. They hold 4 plus gallons. Open your tank and pump it out 4 gallons at a time, takes about an hour. Now you have an empty tank and an open inspection port that you can stick your hand in with paper towels and clean the whole thing out entirerly. When finished you can caulk and seal whole thing up and have a clean tank.

So you still think wouldn't a drain be better? Yah, it would but not in your main cabin. Potential for stink is too great and layout would be a bear. I have the same deal on my Tartan. It may very well be ABYC doesn't allow it and I understand why.

Total project for opening tank, pumping out, cleaning and resealing tank was about 5 hours. You do have to bleed fuel system before you can run boat. I dreaded doing it going in. I wasted some time trying to save money by avoiding buying the extraction system, but in the end I was happy with how it went.

Now i have a nice 12 volt pump extraction sytem for doing all the oil and fluid canges on my boat and that alone was worth it.

SoC
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post #4 of 27 Old 05-19-2013
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Re: Fuel tank drain

A thin skin gasgeted connector will work for a while, but you should remove the tank and MIG (metal inert gas) weld whatever pipe or fitting you desire in place.
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post #5 of 27 Old 05-20-2013
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Re: Fuel tank drain

Years ago I did a test, adding water to a glass of diesel fuel, then adding some Power Service fuel additive. The water soon disappeared from sight.

http://www.powerservice.com/default.asp

Paul T
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post #6 of 27 Old 05-20-2013 Thread Starter
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Re: Fuel tank drain

JimsCAL: We don't have any regs on that down here - or at least none that would apply to me besides "do anything stupid and we'll bust your a$$.."

SoC: Thanks for your reply. Polishing the fuel is a great idea and something I will do, but unless it's working continually it isn't going to get all the water out of the tank, especially after it's been sitting for a week or three.. whereas opening a drain tap will.

Dabnis: Doing that now - but the water comes back out of solution if the boat isn't used for a while. Again, I'd like to take it out once and for all.

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Originally Posted by desert rat View Post
A thin skin gasgeted connector will work for a while, but you should remove the tank and MIG (metal inert gas) weld whatever pipe or fitting you desire in place.
I thought as much.. but thanks for the pointer about MIG.

Any suggestions where to get the fittings?? (please don't say an auto parts store.. I've been down that road already)

Obviously I'd have to put something underneath to catch any drips, but seriously, all of the major Oil Co's use exactly what I've described on the bottom of their filter vessels which could be running anywhere between a vaccuum and over 1000kPa. Is a little unpressurised marine diesel tank a problem - really??

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Last edited by Classic30; 05-20-2013 at 07:19 PM.
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post #7 of 27 Old 05-20-2013
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Re: Fuel tank drain

Quote:
Originally Posted by Hartley18 View Post
JimsCAL: We don't have any regs on that down here - or at least none that would apply to me besides "do anything stupid and we'll bust your a$$.."
There is a very good reason for the regulation. Fittings on the bottom and sides of fuel tanks at some point will leak, hoses crack, clamps vibrate loose, etc. And fuel ends up in the bilge and other places you don't want it. I would not do it even if there isn't a regulation against it.
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post #8 of 27 Old 05-20-2013
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Re: Fuel tank drain

Hartles old man ...... what is your fuel filter setup ? Even though the fuel pickup comes out the top of you tank the pickup itself is down the bottom (I'd have thought). With a decent glass bowl fuel filter (or two) any water will collect in the glass bowl and can be easily drained from there. Glass also gives you a good idea as to how much water is in your system.

Andrew B

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post #9 of 27 Old 05-20-2013 Thread Starter
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Re: Fuel tank drain

Quote:
Originally Posted by tdw View Post
Hartles old man ...... what is your fuel filter setup ? Even though the fuel pickup comes out the top of you tank the pickup itself is down the bottom (I'd have thought). With a decent glass bowl fuel filter (or two) any water will collect in the glass bowl and can be easily drained from there. Glass also gives you a good idea as to how much water is in your system.
It's the usual glass bowl arrangement. Hmm.. you might be right, TD.

It's tricky (read: impossible without a mirror on a stick which I don't currently have) to see just how far the pick-up is off the bottom. I'd have thought the pick-up might be a little ways up to make sure you didn't pull stuff into the filter...?

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post #10 of 27 Old 05-21-2013
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Re: Fuel tank drain

Quote:
Originally Posted by Hartley18 View Post
JimsCAL: We don't have any regs on that down here - or at least none that would apply to me besides "do anything stupid and we'll bust your a$$.."

SoC: Thanks for your reply. Polishing the fuel is a great idea and something I will do, but unless it's working continually it isn't going to get all the water out of the tank, especially after it's been sitting for a week or three.. whereas opening a drain tap will.

Dabnis: Doing that now - but the water comes back out of solution if the boat isn't used for a while. Again, I'd like to take it out once and for all.



I thought as much.. but thanks for the pointer about MIG.

Any suggestions where to get the fittings?? (please don't say an auto parts store.. I've been down that road already)

Obviously I'd have to put something underneath to catch any drips, but seriously, all of the major Oil Co's use exactly what I've described on the bottom of their filter vessels which could be running anywhere between a vaccuum and over 1000kPa. Is a little unpressurised marine diesel tank a problem - really??
Maybe a good water separator until you can get all the water out?

Paul T
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