aluminum water tank refurbish

[cwhofman]

good day everyone, i have a 350 Gallon water tank that looks to have corrosion in the tank. I have opened the tank and pressure washed most of the white deposits from the tank and wanted to see how I can save the tank.

As you might imagine remove such a large tank would require complete destruction of the tank and interior of the boat. I also have a 350 Gallon fuel tank that is next on the list to open up yea !!

Any ideas or experience with such tank refurbishments would be greatly appreciated

any long term result of fixes would be great as well

thanks
Chris

[Pete7]

Does it leak? when I did the same on a previous boat I found a series of small pin holes which were the death knell for the tank and convinced me Aluminium isn't a great material for water tanks. Is there any baffles? how about fitting a couple of plastic tanks inside it if its a real drama to get out.

Pete

[Matt Johnson]

I did one of my 35 gallon tanks awhile ago. Thankfully, two large openings allowed me to reach in with a stainless wire wheel on a 4" grinder to prep the surface. I then wet sanded West Systems* epoxy into the freshly prepared aluminum. Two more coats and I called it good.

You can also blast the inside with a 90 degree tip if you have access.

*while West System isn't FDA approved for potable water use. We'll cured before first use seems to be just fine.

Matt

[cwhofman]

I was looking into the ploy tanks but mounting is an issue.

Hi Matt,

I follow your youtube channel as well

do you have an episode where you tackle the tanks? I did not see it

Do you notice any smell or taste?


Chris

[cwhofman]

trying to upload pictures

[Matt Johnson]

Chris,

Unfortunately, we tackled this before Youtube.... plus, there would have been too many four letter words for that episode anyway We've put water in it, but haven't used it as the marina's water is nasty.

It sucks to do, but can be done with a grinder. If you have access to a soda blaster, I'd recommend that option first.

Matt

[cwhofman]

Did you thicken you epoxy to get it to stick the the sides?

I hear you on the water!! that is why a water maker is in my near future as the quality is questionable really everywhere

thanks Chris

[tkeithlu]

As funjohnson says, clean out the pits, rough the surface, and then multiple coats of epoxy. Understand what's going on here: Aluminum sheet is usually aluminum alloy plated with pure aluminum. Pure aluminum forms a self-protecting aluminum oxide coating, but aluminum alloy corrodes. Pure aluminum sheet would be too soft to be much use. So, note that the welds corrode, and the pits are places the oxide was breached. Therefore, you've really got to either get down to clean alloy or fill those pits so well that corrosion won't continue under your epoxy. If it continues out of sight, one day you're going to find your fresh water in your bilge.All of which says, yes, aluminum is not very good tank material, yes, a smaller tank and a water maker is a combination I prefer (makes chemically better water than our city water), and then carry a few plastic cans of water as backup.

[gjordan]

If you can get into the tank to soda blast then you might want to look into dry ice blasting. It leaves no residue to clean up (other than the corrosion that comes off) and there is nothing to contaminate the rest of the boat. Check with machine shops to find a company that does this. Soda blasting is good, but the clean up would be a major job. Just another idea. Grant

[gkunkle999]

I had pin holes in Al tank. Due to past experience, repairs to Al tanks are only temporary they will leak again. Best bet is to replace. I cut out the old tank (with baffels inside). After a lot of research I replaced it with a bladder. Found a company that made a custome size for for area in the bow of my Hunter. Working great!

[Dave22q]

You might consider placing multiple plastic tanks inside the cut open aluminum tank. It beats me why you want such large tanks instead of a water maker with maybe 100 g of reserve.

[cwhofman]

Thank you everyone for the responses. It looks like I have a few options here.

As far as the size of the tanks... That is the way she came, I'm not sure if the previous owner did not want to add a water maker or what the deal is but they are huge tanks.

If I was to go down the road of adding Plastic tanks inside to old aluminum how would you go about securing it?

Thanks again everyone

Chris

[Dave22q]

I have no idea of your tank dimensions but my thought is that you buy several tanks that will comfortably fit the space and connect them near the bottoms with one piped to your pump. Then tack weld or place wood cross braces to secure the tanks possibly using foam or rubber pads to make a tight fit to the tanks. The exact layout should be easy given the original tank dimensions and a source of stock plastic rank sizes.
Lastly connect your inflow to one of the tanks. The multiple tanks will act as baffles only better. If you want an exterior levels gauge placing the sensors on any tank will be accurate until down to the bottom inch or two.

[tkeithlu]

If you go this route, consider one bladder sized to the bottom of your existing oversized tank, even if that means a custom job. Get hold of a plasma cutter and a ready garden hose, and then very easily slice away the top and sides that you don't need to hold the bladder. A plasma cutter goes through sheet aluminum like a hot knife through butter, and leaves rounded melted edges rather sharp splinters. They don't heat the surround anywhere near as much as does an oxy/acet torch, but they do spray molten metal and fiberglass resin does burn. Make yourself a tray/box to hold your new reasonably sized bladder, and use the rest of the space to mount your watermaker. 140 gallons plus a six gallon per hour watermaker leaves us very happy, complete with hot showers and running both heads with fresh water.

[tkeithlu]

Funny to remember, but I built our boat in a horse pasture/hay field, and kept starting ground cover fires whenever I cut from the inside out with the plasma cutter. The flying splatter would hit dry grass. I finally did a "prescribed burn" of my entire building site, and found several lost parts and tools that had disappeared under the tall grass.