cleaning aluminum water tank

[sorcerer33]

SailingDog: The area I'm in has a previous owner who told me he had flushed the tanks of my boat and left bleach in the tanks to shock them. He succeeded in shocking me too. I'm afraid this was his way of freshening up his tanks - a method that I will not be using in the future.

[sailingdog]

Properly used, chlorine bleach is perfectly safe for shock treating aluminum water tanks. It does have to be thoroughly rinsed from the tanks after doing so. It does not sound like the PO was doing that properly. Some municipalities use enough chlorine in their drinking water treatment to be a problem as well. That would just compound the problem of shock treating the tanks.

Originally Posted by sorcerer33

SailingDog: The area I'm in has a previous owner who told me he had flushed the tanks of my boat and left bleach in the tanks to shock them. He succeeded in shocking me too. I'm afraid this was his way of freshening up his tanks - a method that I will not be using in the future.

[Deadeye]

You mentioned thorough cleaning because you couldn't get the tank out to replace it. Just a thought, but if you can access the top of the tank, you could cut an access opening and use the tank to support and protect a bladder.

Sealing it with epoxy is another option, but I don't have enough personal experience with that to comment on it. West System has some water tank info on their site and their info on other epoxy applications is pretty good.

[CapitanDon]

I just had my aluminum hull cutter in the yard for bottom paint and zincs and was told by the yard manager they had an aluminum hull NOAA vessel in for hull repairs that had integral aluminum freshwater tanks. I was told that when calcium deposits cut off the oxygen to the metal it begins to corrode as happened to this vessel resulting in major repairs to the hull.
I pulled the inspection plate on my integral freshwater tank after hearing this and discovered (to my horror) what looked like seaweed in the tank. apparently when this boat was built or re-fit, a coating was sprayed inside the tank to possibly prevent calcium deposit build up??. I have owned the boat several years (A custom build, I am the 4th owner) and have been occasionally adding a cup or so of household bleach to the water to kill any bacteria. (big mistake!) Apparently the bleach dissolved most of the coating leaving quite a mess in the tank as well as some minor pitting of the tank walls. So I have a similar (or worse) situation. My tank also cannot be removed. To clean it will be difficult due to baffels and the only access is the inspection plate (about 18" X 24"). Going in through the outside hull is also near impossible due to an encapsulated concrete filled ballast keel. (the tank is 40Gal centerlined amidships) The only way I see to access it is by removing the cabin sole above the tank (nicely done teak & cherry) Then I think the best option is sand or soda blast to clean and remove the pitting. From what I have learned as long as oxygen is present and calcium not allowed to build up the tank will last.
I also admit to not being an expert in electrollisis (I cant even spell it!) and corrosion in aluminum before buying a boat with aluminum tankage.

Any advise or suggestions would be appreciated.

[sailingdog]

While you'd be better off starting your own thread... I'd point out that adding chlorine bleach to your water system on a regular basis is a really bad idea if you have an aluminum tank... I would highly recommend discontinuing the practice. Chlorine bleach attacks the aluminum.

Cutting open the tank and replacing it with flexible bladder or a custom plastic tank might be better options than trying to clean and restore this tank. Without knowing how serious the pitting is, there is no way to see how severe the damage to the tank is, and trying to salvage the tank may just increase your costs overall.

Originally Posted by CapitanDon

I just had my aluminum hull cutter in the yard for bottom paint and zincs and was told by the yard manager they had an aluminum hull NOAA vessel in for hull repairs that had integral aluminum freshwater tanks. I was told that when calcium deposits cut off the oxygen to the metal it begins to corrode as happened to this vessel resulting in major repairs to the hull.
I pulled the inspection plate on my integral freshwater tank after hearing this and discovered (to my horror) what looked like seaweed in the tank. apparently when this boat was built or re-fit, a coating was sprayed inside the tank to possibly prevent calcium deposit build up??. I have owned the boat several years (A custom build, I am the 4th owner) and have been occasionally adding a cup or so of household bleach to the water to kill any bacteria. (big mistake!) Apparently the bleach dissolved most of the coating leaving quite a mess in the tank as well as some minor pitting of the tank walls. So I have a similar (or worse) situation. My tank also cannot be removed. To clean it will be difficult due to baffels and the only access is the inspection plate (about 18" X 24"). Going in through the outside hull is also near impossible due to an encapsulated concrete filled ballast keel. (the tank is 40Gal centerlined amidships) The only way I see to access it is by removing the cabin sole above the tank (nicely done teak & cherry) Then I think the best option is sand or soda blast to clean and remove the pitting. From what I have learned as long as oxygen is present and calcium not allowed to build up the tank will last.
I also admit to not being an expert in electrollisis (I cant even spell it!) and corrosion in aluminum before buying a boat with aluminum tankage.

Any advise or suggestions would be appreciated.

[Snboard976]

I wonder if I'm looking at aluminum oxide or calcium deposits in my aluminum tank? Removing the tank is not an option - teak & holly floor would have to be removed as well as sink cabinetry etc. Baffles in the tank make installation of a liner or bladder near impossible. I was told by someone with a knowledge of chemistry to use the product that is placed in a shower and sprays automatically to kill mold. He also said hot water was the best wash to use.

[sailingdog]

What do the deposits look like? Aluminum oxide is usually a greyish color... but tends not to form except as a layer coating the metal. If the deposits are collecting, it is likely aluminum chloride instead, which is often a whitish powder.

Many of the products that are used to kill mold/mildew are not safe for use in potable water systems.

Originally Posted by Snboard976

I wonder if I'm looking at aluminum oxide or calcium deposits in my aluminum tank? Removing the tank is not an option - teak & holly floor would have to be removed as well as sink cabinetry etc. Baffles in the tank make installation of a liner or bladder near impossible. I was told by someone with a knowledge of chemistry to use the product that is placed in a shower and sprays automatically to kill mold. He also said hot water was the best wash to use.

[wenger230]

Now, This is becoming very important to get installed a rain water tank in a house to save the water and making the country save and secure in future.

water tank

[mitiempo]

Were you looking for a sailing forum?