Aluminum Water Tank Corrosion ?

[Pete7]

We had this on a previous power boat. To make matters worse the shower drain leaked so the aluminium tank constantly sat in a pool of water in the bilge. Also contributing was the wires to the shower pump were also under the bilge water and only crimped with car connectors.

Took the tank out only to find all that horrible white stuff inside and then dozens of tiny pin holes in the tank when I pressure washed it out. I was going to try and repair the tank but gave up and replaced it with a flexible tank. It might not have lasted as long but was cost effective.

Plastic fuel and water tanks every time for me.

Pete

[Hud3]

Originally Posted by gettinthere

Hud

How much water could you treat with one filter? How often did you change filters?

Thanks for this info.

The activated carbon in the filter will last a long time, but it depends on how much chlorine is in the water that passes through it, and how many gallons of water you treat per year. I'd suggest you change the filter once a year whether it needs it or not. They'd probably last several years for most folks, but they're cheap.

My tank was the 5083 alloy, but it still corroded. Not enough to make me worry about it failing, but enough to be an irritation because of the periodic clogging of the pump screen and faucet aerators.

[Bill_E]

First, aluminum was implicated in Alzheimer's many years ago because there were some cases where high levels of aluminum were found in Alzheimer's patients. Well, correlation isn't causation! And, that theory is no longer believed. But the urban legend lives on.

There are a bunch of threads on the board about using peroxide as a disinfectant. Here are a few of them.
Fresh Water Tank Cleaning
Purification of Water Tanks
Hot Water Stinks

I'm getting about ready for a major cleaning of my freshwater system and have been looking for food grade (35%) hydrogen peroxide on the internet. It's definitely available by mail. At that concentration, I'd be pretty careful in handling it. Wear rubber gloves, long sleeves, goggles. One good thing about hydrogen peroxide is that the final products, after cleaning are water and oxygen (in very small amounts so not dangerous unless you are trying to make rocket fuel in your closet). There is a potential for some oxidation of rubber parts in the system but I doubt if it's serious. In any case, chlorine bleach is pretty rough on rubber, too.

Peggy Hall (The Headmistress) is the source of all information about marine water systems!! Here's a link to an old version of her advice. There is some discussion of whether she still approves of this link.
the boatbuilding.community - Marine Sanitation: Fact vs. Folklore
And here's another link to one that she wrote in 2003.
http://home.online.no/~lha-h/forum/phall.pdf

And finally, you can purchase her book:
Amazon.com: Get Rid of Boat Odors: A Boat Owners Guide to Marine Sanitation Systems and Other Sources of Aggravation and Odor (9781892399151): Peggie Hall: Books

Get Rid of Boat Odors

If anyone has read it or has a copy, I'd like to get a review. I'm thinking of buying one.

Bill

[gettinthere]

thanks Hud, we'll implement your idea in the spring

[HotRod]

In general, if you have corrosion in an aluminium tank, it's not a suitable alloy of aluminium that has been used to build it.
If you get a clogged filter due to corrosion, you have not just a bit of corrosion but more like an infection, there is no use in trying to rinse that out. It will just continue until you have a sieve of a tank.
If you use a coalfilter you need to replace this every year, no matter how many liters that run trough it... After a short while bacterias will grow in it - the filters has been tested and discussed in may labs around the world.
The only filters that has been proven good cost a small fortune, but last only for a few months after opened from the sealed container.

Why do you think that big vessels with alu tanks coat the inside of the tank with a type of concrete to make sure that the water does not get contaminated by the alu? This goes also for the vessels with ordinary steel tanks (not stainless steel).

[boatman61]

I don't know about chlorine treatment... never given it much of a thought but I do know from experience that mains water in the States is pretty crap by EU standards...
When I filled my tanks in NC after two weeks it started sprouting fungus... yuuk.. anyway I did what I normally do in the Carib and other places I'm unsure of the quality... a couple of capfuls of plain household bleach per tank.. or white vinegar..... sterilizes it a treat...
Every time I came out of the B/yard shower I smelt like I'd been swimming in the Neuse...

[wimpy]

I have read that chlorine dioxide is suitable for disinfecting aluminum tanks as it does not react with aluminum the way chlorine does. I cant seem to find quantities large enough to do my tank. It is sold as a disinfectant that hikers use to make water safe to drink.It is also used commercially to clean large aluminum tanks.Any one have any experience with it.

[St. Elsewhere]

If it is due to biological activity bleach would be an answer. 5000l would take a lot of it, perhaps ten to twelve gallons. If there is an access panel you could empty it and scrub it down with a brush and bleach.

If the problem is hydrogen sulfide in your water source this will not help.

[bottomsjohn]

My aluminum hot water tank exhibits a very stong chemical odor, a little like formaldehyde. This odor is not at all evident at the cold water taps. The boat is new to me with the previous owner not available so I have no idea if the odor existed before I changed out the 120 VAC element to a 100 watt VDC element. No aluminum oxide granules have been noticied despite use of chlorinated water, but the acrid chemical order is worrisome. Any thoughts on the cause? Thanks

[Bill_E]

I wouldn't think that the aluminum and aluminum salts would have much detectable odor. I wonder if the warm (hot) water is dissolving some plasticizer or other component from some of your "rubber" or plastic tubing in the hot water system. You might try checking through your entire hot water system, following the tubing to see if there are any parts that might "off gas". I know that a lot of people use inappropriate components so you might have some tubing that is not designed for hot, potable water.

Although I know I have an aluminum water holding tank, I'd never thought much about my hot water tank. I'll have to check it out now. But, of course, filtering my water and not using chlorine compounds in my water system should protect it in any case.

[bottomsjohn]

Thanks for the response. All of my hoses are type suitable for potable water. The only thing that I have changed is the 120VAC element to a 12VDC element to be able to use the excess amps from a large solar panel. My initial thought was that high heat was causing some chemical reaction, but it has been cloudy for the last several days resulting in only slightly warm water, but the same odor. No odor exists at the cold taps.
Maybe I will pull the new element and stick in a pan of the same water to see if an odor develops!