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Old 26-09-2020, 22:56   #1
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Aluminum water tank leak

I have an aluminum water tank">fresh water tank with a leak at the valve stem. It's impossible to try to weld it where it is and it would take destroying my boat to get the tank out. Any suggestions with epoxy? JB weld? Thanks.
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Old 26-09-2020, 23:13   #2
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Re: Aluminum water tank leak

I have never done n aluminium tank repair, but the diesel tanks on my boat are both aluminium coated with epoxy on the outside. So i would assume that an epoxy repair should work, but make sure you clean it with MEK, not acetone
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Old 27-09-2020, 08:38   #3
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Re: Aluminum water tank leak

I was going to use acetone, what's the difference? Also, somebody previously tried to repair it with a clay like epoxy. I was just going to try to chip that off. Any other suggestions?
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Old 27-09-2020, 08:58   #4
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Re: Aluminum water tank leak

MEK will dissolve epoxies, while acetone will not.

Consider: Let's go back to that previous repair. Did the epoxy adhere to the top of the tank? If so, sanding it down and building up from there is an option. Another option is sanding the top of the tank near the tap with coarse sandpaper, making a very clean and rough surface that your epoxy can adhere to. Then, don't just build a little volcano around the joint. Make a cylinder of epozy maybe two inches in diameter and deep enough to allow you to cut pipe threads. Remount the tap. Your goal is to make a mount that can stand the lateral force that broke it in the first place.
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Old 27-09-2020, 10:10   #5
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Re: Aluminum water tank leak

Thanks for the tip. The leak is at the bottom of the tank. I have just shut the valve to keep water from entering it from my other tank.
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Old 27-09-2020, 10:35   #6
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Re: Aluminum water tank leak

Hello I am new here. I have a similar problem in one of my five ss water tanks. It has developed a leak and is under the beautiful teak galley and not easily removable. I have valved it off and still have 250 gallons of capacity left. I probably will try to repair if i can reach the spot through the access port. I have done a similar repair that lasted before with JB Weld. Failing this I am looking at putting a flexible tank inside the existing one. Some surgery to the old tank top will be nessary to allow the inlet and vent hose in.
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Old 27-09-2020, 10:35   #7
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Re: Aluminum water tank leak

Quote:
Originally Posted by Pfeiffer View Post
I have an aluminum fresh water tank with a leak at the valve stem. It's impossible to try to weld it where it is and it would take destroying my boat to get the tank out. Any suggestions with epoxy? JB weld? Thanks.

Pictures.


The valve stem is part of the valve, so I'm guessing you mean the coupling half that is welded into the tank.


Another thing to consider is cleaning and inspecting the inside of the tank. You may find that it is riddled with corrosion and this is simply the first hole. I hope not. Or is it a crack due to operational or construction stress?



Can you reach it from the inside?


Aluminum is not the easiest material to bond. You need to sand it white and bond before a fresh layer of corrosion forms. If it is a stress crack, the repair needs both area and a flexible reinforcement material, such as a polyester scrim.
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Old 27-09-2020, 10:50   #8
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Re: Aluminum water tank leak

If there is a stress crack there, it needs to be stop drilled before reair.

I didn't understand this to be on the bottom. That does change some things, the first being thinwater's point that you may be facing a bunch of pin holes. In a hard to remove tank, one route for solving that problem is draining, drying, and then pouring in a liner for the bottom.

Adhesion: I was thinking about this a few minutes ago, and thought that you could really anchor that epoxy by inserting a few screws, with their heads sticking up, around the hole. Then build up the epoxy.

Then, another route to consider: attach a thick aluminum plate, predrilled and threaded, with a gasket and sheet metal screws..

Several ways to skin this cat. Good luck with it.
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Old 27-09-2020, 10:53   #9
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Re: Aluminum water tank leak

I did a repair on the bottom of my aluminum water tank 5 or so years back, still holding fine. Used West Gflex, cleaned the hole with a small drill bit, agressively cleaned the surrounding area, mixed up a paste with aluminum powder (suspect most quality additives would work as well), used visqueen and plywood to hold the patch in place until hard.


I inspected the inside of the tank before hand. Some small localized corrosion cells but most of the tank looked pretty good for 25 years.


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Old 27-09-2020, 11:40   #10
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Re: Aluminum water tank leak

How you effect a temporary repair (even a hopefully long term temporary repair) will depend on the exact location and type of leak.

Here are some thoughts:

A fracture at a fitting could be the hardest but several ways are possible, including (which might be the best) to remove the fitting and drill and thread a new bigger fitting, or, apply an aluminum patch on the outside, with screws and sealant, and thread a new fitting onto that patch.

A more common type of leak in aluminum tanks, particularly at the bottom where possible seawater corrosion may have occurred, is large area of corrosion with several pinholes or future pinholes. I have cured this type of leak with a coating of epoxy (on the inside) applied after cleaning and sanding. This could last quite a while.

Long term a permanent solution will be a new tank or an inserted bladder, however that will result in a loss of capacity. Frankly I have no experience with this although lots of people speak of it. Perhaps others on this forum have experience with inserting rubber bladders.

In my own case I have recently replaced two water tanks with custom made stainless steel. Big job but it should last a while but this is the second time, the first, 15 years ago, failed with poor welds and stainless steel rusting! I am lucky that all of our tanks, water, fuel and holding, are easily accessible can remove any tank in less than four hours, but dang I hate doing it.
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Old 27-09-2020, 12:33   #11
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Re: Aluminum water tank leak

Hi. Could you post a photo please. If not a drawing. You say you canít weld it in place...why. TIG guns are small and fit in really tight places. If itís at the bottom of the tank as suggested by others, you might have a series of ready to fail pin holes. I wonít comment on a fix till I have a better understanding.
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Old 27-09-2020, 13:46   #12
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Re: Aluminum water tank leak

Epoxy is good, but often inflexible.
Likely a majority of aircraft use the wing itself as a fuel tank, the wing is of course full of holes from rivets and is many pieces of metal put together.
To seal it and make a fuel tank that won’t leak, there is a special sealer used.
I’d use it to seal an aluminum water or fuel tank myself.
It comes in an A mix which is thin like 5200, and a B mix which is thicker.
It also comes from 1/4 to 4 with the numbers representing pot life 1/4 hour to 4 hours.
Most often B2 is used.
https://www.aircraftspruce.com/catal...prosealant.php
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Old 27-09-2020, 15:14   #13
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Re: Aluminum water tank leak

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Originally Posted by a64pilot View Post
Epoxy is good, but often inflexible.
Likely a majority of aircraft use the wing itself as a fuel tank, the wing is of course full of holes from rivets and is many pieces of metal put together.
To seal it and make a fuel tank that wonít leak, there is a special sealer used.
Iíd use it to seal an aluminum water or fuel tank myself.
It comes in an A mix which is thin like 5200, and a B mix which is thicker.
It also comes from 1/4 to 4 with the numbers representing pot life 1/4 hour to 4 hours.
Most often B2 is used.
https://www.aircraftspruce.com/catal...prosealant.php
Good choice, they also have AC 236 B2 which is also a good product for the same purpose used in Van's Aircraft and also sold by them..it gives you a longer work time and it's also a lot less money
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Old 27-09-2020, 15:18   #14
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Re: Aluminum water tank leak

Do you think the above sealer would work on a SS tank?
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Old 27-09-2020, 16:05   #15
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Re: Aluminum water tank leak

Use a wire brush to rough up the crack/leak, then use some Bondo (two coats) to make the repair. Used that method for gas tank repair and it lasted several years!
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