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02-16-2021, 02:29 PM
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#1
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Veteran Member
City: New Orleans
Vessel Name: Tortuga Roja
Vessel Model: Oceans PT Sundeck 46
Join Date: Dec 2019
Posts: 52
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Diesel tank leak
I have a strange situation with a diesel tank leaking.
Diesel in the sump. Oh no. Cleaned it up. Seems to be at bottom of 200 gal steel tank. Emptied, washed, emptied. Air test. 4 lb 2 days. Hmmm no leaking. Added 2 8 inch inspection holes cleaned again. Air test. No leaking. Added fuel. No leak. Came back 2 days later gallon of fuel on the floor. Emptied tank washed, air test
No leaking! HELP!
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02-16-2021, 02:57 PM
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#2
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Moderator Emeritus
City: Au Gres, MI
Vessel Name: Black Dog
Vessel Model: Formula 41PC
Join Date: Jul 2015
Posts: 21,131
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Could a fuel hose be weeping? Put some paper towels around where you suspect a leak and they will show the leaks. Put them all around and see which ones get wet.
__________________
Boat Nut:
If you are one there is no explanation necessary.
If you aren’t one, there is no explanation possible.
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02-16-2021, 03:23 PM
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#3
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Guru
City: Between Oregon and Alaska
Vessel Name: Charlie Harper
Vessel Model: Wheeler Shipyard 83'
Join Date: Jun 2016
Posts: 3,021
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I've had leaks where a fuel line or hose wore a hole where it went thru a clamp hanger. Engine vibration over time wore a small hole. Since the hole was caused by the hanger, the hole was against it and didn't always leak. Eventually I reasoned that it leaked at night when everything was cooled down. The fuel line contracted slightly and opened the hole.
Best way to fine it is with air pressure in the line and listen for the leak.
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02-16-2021, 04:37 PM
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#4
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Guru
City: Long island
Vessel Model: Eastern
Join Date: Aug 2018
Posts: 632
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If there is sludge in the bottom, it may pass a pressure test but not a leak test
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02-16-2021, 04:47 PM
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#5
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Guru
City: Oconto, WI
Vessel Name: Best Alternative
Vessel Model: 36 Albin Aft Cabin
Join Date: Oct 2012
Posts: 3,145
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Sounds like a syphon going on with a fuel line.
pete
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02-16-2021, 05:25 PM
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#6
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Guru
City: .
Vessel Name: GOTCHA
Vessel Model: Hatteras 58 LRC
Join Date: Jun 2019
Posts: 1,100
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Try capping all of the fuel tank outlets, and then pressure test again. If that works okay try pressure testing each of the fuel lines and filters. Thake it one step at a time until you find the leak.
Dave is correct WHITE paper towels laced out everywhere will help spot the leak.
__________________
Captain F. Lee - R.P.E.
USCG 200 GT Master
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02-16-2021, 09:27 PM
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#7
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Veteran Member
City: New Orleans
Vessel Name: Tortuga Roja
Vessel Model: Oceans PT Sundeck 46
Join Date: Dec 2019
Posts: 52
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I wish it was as simple as that. All fuel lines are closed. Air vent closed, fill cap closed. One day it leaks, the next day it doesn’t. Paper towels are good today, tomorrow I may need a bucket!
I left 5 # air pressure on it today. I’ll check it again tomorrow. It has baffled me. The leak comes from the bottom of the tank. Or the back and then runs to the bottom front. Next will be to fill it with water and see if that leaks out. Thank you all for your input. Please don’t stop sending ideas...
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02-16-2021, 10:08 PM
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#8
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Moderator Emeritus
City: Au Gres, MI
Vessel Name: Black Dog
Vessel Model: Formula 41PC
Join Date: Jul 2015
Posts: 21,131
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You said you cleaned the tank out several times so I don’t think it is a layer of crap on the bottom of the tank plugging up some pinholes and they leak intermittently, but that would be my guess with the latest info you have provided. If the tank leaks when all the fuel hoses turned off then you have a leaking tank. The solution is to either replace the tank or try one of the tank sealing products and see if you can find one that works. Who knows, I have read posts that said the sealing products work and others that say they don’t. The sure fix is a new tank, but expensive. How old is the tank? Good luck.
__________________
Boat Nut:
If you are one there is no explanation necessary.
If you aren’t one, there is no explanation possible.
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02-17-2021, 03:35 PM
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#9
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Guru
City: .
Vessel Name: GOTCHA
Vessel Model: Hatteras 58 LRC
Join Date: Jun 2019
Posts: 1,100
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Can the tank be removed without tearing the boat apart?
The pics look like the tank maybe coated with something.
If they are S.S. then no coating is needed.
If they are coated it may be hiding further problems.
__________________
Captain F. Lee - R.P.E.
USCG 200 GT Master
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02-17-2021, 04:58 PM
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#10
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Technical Guru
City: Wilmington, NC
Vessel Name: Louisa
Vessel Model: Custom Built 38
Join Date: Jan 2014
Posts: 6,194
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Pressure testing an empty tank with air is problematic. The air under pressure is partially compressed, and there is a lot of volume, it would have to be a big leak to show up as a reduction of pressure. Also, pressure reading will vary a bit with temperature changes.
When we pressure tested with air, we would hold the pressure and "snoop test" (dilute soap solution) to look for bubbles. Not practical in a coated, installed tank.
Since you have access panels, I'd look into sealing the inside. Unfortunately I am no help on the best method.
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02-17-2021, 05:20 PM
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#11
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Guru
City: Oconto, WI
Vessel Name: Best Alternative
Vessel Model: 36 Albin Aft Cabin
Join Date: Oct 2012
Posts: 3,145
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Fiberglass fuel tanks are built of numerous layers of fiber and resin. A leak in any one area does little to indicate where the leak starts. If the glass is delaminating the fuel can trickle a long was before it escapes the tank. Although your tanks look sound I suspect they are delaminating. Please tell me the dark grey and light blue colors are a trick of lighting. If not, they are saturated and ready for replacement
pete
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02-17-2021, 06:09 PM
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#12
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Veteran Member
City: New Orleans
Vessel Name: Tortuga Roja
Vessel Model: Oceans PT Sundeck 46
Join Date: Dec 2019
Posts: 52
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No, it’s take out the engines or through the side. Air test again today
9:30 am 5 pounds 3 pm 5 pounds.
Tomorrow I’ll try a vacuum test.
Colors are light shading.
After vacuum test, I’ll try colored water test. At my wits end!
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02-17-2021, 06:14 PM
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#13
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Guru
City: Long island
Vessel Model: Eastern
Join Date: Aug 2018
Posts: 632
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Carful with a vacuum test . You may make a portable tank out of it.
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02-17-2021, 06:17 PM
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#14
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Veteran Member
City: New Orleans
Vessel Name: Tortuga Roja
Vessel Model: Oceans PT Sundeck 46
Join Date: Dec 2019
Posts: 52
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Quote:
Originally Posted by Arc
Carful with a vacuum test . You may make a portable tank out of it.
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Yeah, my vessel engineer said 1 pound should be enough.
I lowered the pressure this afternoon to two pounds in hopes too much pressure is sealing the leak up
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02-19-2021, 08:32 AM
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#15
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Veteran Member
City: toronto
Join Date: Aug 2020
Posts: 49
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When you air test it is there fuel in the tank or are you hoping to push air out of the hole? Just wondering thanks and good luck
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02-19-2021, 04:56 PM
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#16
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Veteran Member
City: New Orleans
Vessel Name: Tortuga Roja
Vessel Model: Oceans PT Sundeck 46
Join Date: Dec 2019
Posts: 52
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Air test was just air. Today I put in 80 gallons of fluorescent water and 4 pounds of air. Tomorrow we will see.
I had an old welder tell me that he used to work in vessels that x rays could not find a leak in, but diesel could! Sooner or later I’m going to figure this out. Through friends daughter who is a coatings specialist for the navy, I hopefully figure out what to coat the inside of the tank with......time will tell
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02-19-2021, 06:07 PM
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#17
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Guru
City: Gulf coast
Join Date: Aug 2016
Posts: 2,269
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Quote:
Originally Posted by fgarriso
Dave is correct WHITE paper towels laced out everywhere will help spot the leak.
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I actually find that the brown paper towels, the cheap gas station kind, show leaks better. They change color from light-tan to dark brown with a drop.
Wet white somehow seems to look like dry white. At least to me.
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02-19-2021, 07:07 PM
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#18
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Guru
City: Gibsons, B.C., Canada
Vessel Name: Island Pride
Vessel Model: Palmer 32'
Join Date: Oct 2007
Posts: 4,409
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I have found the blue Scot or similar blue towels show even a small bit of wetness very distinctly. The white not so much.
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02-20-2021, 01:13 PM
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#19
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Guru
City: .
Vessel Name: GOTCHA
Vessel Model: Hatteras 58 LRC
Join Date: Jun 2019
Posts: 1,100
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If removing the tanks is out of the question then your only solution is coating the inside. That will require removing all lines, vents, and valves. Then install brass plugs everywhere . You will need the brass plugs installed so the sealer coating won't seal up the ports.
https://www.kbs-coatings.com/tank-sealers.html
__________________
Captain F. Lee - R.P.E.
USCG 200 GT Master
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02-20-2021, 01:33 PM
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#20
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Guru
City: .
Vessel Name: GOTCHA
Vessel Model: Hatteras 58 LRC
Join Date: Jun 2019
Posts: 1,100
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After looking at the pics again the tanks appear to be fiberglass. If that is correct do to delamination issues with fiberglass the leaks could be coming from anywhere. The only solutions is cutting the hull sides out to remove the tanks, and then reglassing the hull. Or, sealing the the tanks from the inside. Pressure testing a fiberglass tank may not work do to the pressure sealing up the laminations
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Captain F. Lee - R.P.E.
USCG 200 GT Master
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