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Old 22-05-2020, 14:27   #1
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Repairing a Leaking Aluminum Water Tank

After 17 years of service, our 46 gal aluminum water tank is leaking. My visual inspection through the inspection ports indicates rusting of the welds.

Are there any repair methods that can be accomplished without removing the tank from the boat? I was wondering if there is a liquid that can be poured into the dry tank to about 3/4 inches that would cover and seal the welds and eventually harden creating a new base for the tank?

If there in no good in-situ repair and the tank must be removed from the boat, what repairs can be accomplished short of fabricating a new tank? Is it possible to re-weld the joints?

Your ideas would be much appreciated.

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Old 22-05-2020, 14:44   #2
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Re: Repairing a Leaking Aluminum Water Tank

Hello, agaronzik,

I'm a little confused about "rust" for an aluminum tank. Rust is what iron and steel do. It is iron oxides of different chemical properties. Aluminum, however, reacts with the chlorine in tap water, and will pit and also form lumps of aluminum oxides.

So, I'll guess that what you have is pinholes in your welds. One time we had an aluminum diesel tank that developed a pinhole leak at its lowest point, and for a field repair, Jim cut a beer can and formed it to fit the tank, then bonded it on with epoxy.
Now, I believe there are food grade epoxies that you might use for such an endeavor.

However, the problem in your case is that the tank may be riddled with pinholes. In which case, the easiest option might be to cut off the top of the tank, and put in a new polyethylene one of approximately the same size. If you still want to have aluminum water tanks, you should consider prefiltering the water you use in them. We have a friend who does this routinely, using two liter size charcoal filters between the tap and the tank fills.

Hope this helps.

Ann

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Old 22-05-2020, 15:15   #3
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Re: Repairing a Leaking Aluminum Water Tank

My secondary water tank developed some small holes from internal corrosion. I thought about replacing the tank with a plastic one, but I would have had to cut up the 75 gal. aluminum tank into pieces in order to remove it.

I cut a 6" hole in the top of the tank, completely dried out the interior, removed the dissimilar metals used for the outlets, and sanded/wire brushed the area of corrosion, cleaned with alcohol, and then used JB Weld Marineweld (which is non-toxic) to coat the area around the corrosion as well as the welded joints in that area and let it dry for 72 hours.

I replaced the brass fittings with Marelon fittings, then flushed the tank twice, then installed a watertight 6" access plate.

Fortunately, once I was able to look inside I saw the corrosion was very localized. Good to go for over a year now.
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Old 22-05-2020, 16:01   #4
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Re: Repairing a Leaking Aluminum Water Tank

If you can access the area from the outside, clean the area around the leak (SS wire brush, coarse sand paper), use a small drill to clean out the hole. Mix up some West G Flex Epoxy and spread it in and around the repair. Cover the area with visqueen and clamp/ force some wood to hold the visqueen and epoxy in place.


I have repaired non structural aluminum this way and it lasts for years.


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Old 22-05-2020, 16:30   #5
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Re: Repairing a Leaking Aluminum Water Tank

Cut an access hole and install a rubber bladder
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Old 22-05-2020, 16:47   #6
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Re: Repairing a Leaking Aluminum Water Tank

Interested in this too. I have a stainless water tank with 6" access plate under my v berth. I suspect i have a pinhole somewhere near the outlet as when i fill the tank i get a very tiny water streak in the bilge.

I've thought about using UV dye to determine if it is in fact coming from there or simply a chain locker drain

Was thinking of drying the tank over the winter and applying a food grade goo in the hopes it finds the pinhole. Rather not destruct the v berth just to yank the tank.

If i did, I'd just TIG weld it by craning in my TIG machine as i don't think i could remove it in 1 piece through the cabin.

My leak is so tiny its more of an OCD annoyance than anything.
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Old 22-05-2020, 18:28   #7
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Re: Repairing a Leaking Aluminum Water Tank

Why just cut off the top of the tank to put a PE tank inside it, Ann? If access permits doing that, why not just remove the aluminum tank altogether and replace it with a PE tank?


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Old 22-05-2020, 19:11   #8
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Re: Repairing a Leaking Aluminum Water Tank

To coat the bottom of the tank it needs to be clean. No sand, algae, etc. And light sanding helps.
You could try:
https://www.international-marine.com...-tank-coatings
Potable Water Tank Epoxy Coating System
Or if the tank is clean and dry, you try West System epoxy. I've built water tanks using it. It usually takes a soaking with water and baking soda to mellow the taste.
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Old 23-05-2020, 10:15   #9
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Re: Repairing a Leaking Aluminum Water Tank

Take a look at this

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Old 23-05-2020, 10:56   #10
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Re: Repairing a Leaking Aluminum Water Tank

Hi. Repair Welding aluminium is possible but very specialised work. The work has to be thoroughly clean to remove oxides but that is not main problem. As it conducts heat so well, the whole workpiece will need to be heated to near welding temperature, which i believe is not much less than Melting point. I cant see you could do that in situ hence all the non welding replies on here.
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Old 23-05-2020, 13:49   #11
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Re: Repairing a Leaking Aluminum Water Tank

I am in the process of repairing my aluminum tank with many small holes. I cut 4 access holes in the top, cleaned it with vinegar, wire brushed and sanded where I could reach. There is a cross shaped baffle which makes 4 sections plus baffels on the sides. I coated the inside with 6 coats of West epoxy and am waiting for a few days to fill it. I started praying yesterday.
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Old 23-05-2020, 13:59   #12
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Re: Repairing a Leaking Aluminum Water Tank

There's no rust I dont imagine if Aluminum.
I like the idea of a plastic tank inside the old tank.

It's probably buried in a Passport, mine was. If not just remove the tank and have a new bottom welded onto it... it's almost always one of the bottom welds or the bottom plate corroded on Aluminum. I've seen this done. There's not "preheating " of the whole tank necessary. (that's if cast aluminum)

But your Passport has an aluminum tank? I thought they were SS?
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Old 23-05-2020, 21:01   #13
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Re: Repairing a Leaking Aluminum Water Tank

If your tank is broken by stress concentrations at corners through being incorrectly welded or poorly supported it is fixable. If it is the wrong alloy for the purpose, or suffering from galvanic corrosion through copper piping being part of the water system, it needs to be tested to see if it is worth fixing.

If it has a decent sized inspection port it can be patched within, or even used to house a water bladder if there are no sharp protuberances inside it.

Personally, if it is corroded elsewhere I would junk it and replace it with a new high density polythene tank set securely strapped into a plywood carpeted well anchored structure, but that is just me. I hate water tankage located below the cabin or a saloon soles. I like it below water line, but not right down in the bilges.

If you have a water maker aboard, you need about one hundred gallons of storage capacity maximum and fifty gallons would probably do.
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Old 23-05-2020, 21:13   #14
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Re: Repairing a Leaking Aluminum Water Tank

I used to weld aluminium using oxy acetlene and special fluxes and rods--beware of some of the low temperature aluminum welding rods. Some contain bismuth and some antimony, some lead or tin. Aluminium needs to be welded with ALUMINIUM.

The temperature is critical. I used to wipe each side of the weld with Sunlight soap, but any pure unscented sodium stearate laundry soap, (not a detergent) would serve. When this streak of soap turns brown--you are ready to begin to weld--using a slight carburising flame. You need practice.

If you have a TIG welder you can do the job even more effectively.

Lotsa luck!!
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Old 23-05-2020, 21:18   #15
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Re: Repairing a Leaking Aluminum Water Tank

On the same subject (leaky water tank) but made from different material. I need a solution...I have a Plastimo 100 litre plastic water tank that is leaking in drips at a time. I think it is the tank outlet connector for the hose, the problem is that the tank is it build into the galley cabinets and the tank connector is on the bottom of the tank.

It would be very expensive disruptive and time-consuming to take the galley apart to find the leak. I do have a 6" inspection port under the stove cabinet recess - Question) does any member know if there is a product say like a radiator stop leak, which would the same job to stop leaking for small fresh water tanks? I hope there is a solution in Say a product you mix with drinking water letting the leak carry the material to block the mystery leak. Then drain the tank dry and refill?

Thanks, Keep up the good work! Kryg Skoiern IV



Quote:
Originally Posted by JPA Cate View Post
Hello, agaronzik,

I'm a little confused about "rust" for an aluminum tank. Rust is what iron and steel do. It is iron oxides of different chemical properties. Aluminum, however, reacts with the chlorine in tap water, and will pit and also form lumps of aluminum oxides.

So, I'll guess that what you have is pinholes in your welds. One time we had an aluminum diesel tank that developed a pinhole leak at its lowest point, and for a field repair, Jim cut a beer can and formed it to fit the tank, then bonded it on with epoxy.
Now, I believe there are food grade epoxies that you might use for such an endeavor.

However, the problem in your case is that the tank may be riddled with pinholes. In which case, the easiest option might be to cut off the top of the tank, and put in a new polyethylene one of approximately the same size. If you still want to have aluminum water tanks, you should consider prefiltering the water you use in them. We have a friend who does this routinely, using two liter size charcoal filters between the tap and the tank fills.

Hope this helps.

Ann

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