Barnacles in fresh water tanks

[Mark Maulden]

Well, not really. But, ~3yrs years ago when we bought the boat ('79 vintage), I put access plates on the fuel tank and both water tanks. The water tanks had some very hard white substance on the interior surfaces (perhaps leached calcium??). We knocked everything off we could and found out there was pitting underneath. Last year we actually lost a water tank (leaks) and replaced it. I've now just completed replacement of the other water tank (and fuel tank) for peace of mind. So, my question is if there is anything to prevent this white stuff from forming and adhering to the interior surface? And yes, all fill/vent lines replaced. Plumbing is CU. Have not found anything with searches....

 

[Mark Maulden]

Re: barnacles in fresh water tanks...

Oh ya.. Tanks are aluminum

 

[Steve Dion]

Re: barnacles in fresh water tanks...

Mark: I don't think you would have this issue with a poly tank. I also think that there may be issues if your water supply is highly chlorinated. The new tank will probably last another 20+ years.

 

[Crazy Dave Condon]

Could it be from filling tanks with fresh water say for example from a well source without going thru a filtering process. I ran into that as well

 

[capta]

My thought would be that somewhere along the line water was put in the tanks with a higher salt content than usual. If you have a watermaker, perhaps it's from that, or the shoreside water was contaminated by something like storm surge.

 

[rgranger]

So, my question is if there is anything to prevent this white stuff from forming and adhering to the interior surface? ......

I'd guess flushing with a few gallons of cheap vinegar about once a season would really help. Put in the vinegar, fill the tanks, let sit overnight, flush out with fresh water until the vinegar smell is gone.

 

[zeehag]

calcium is a hard water deposit. use vinegar to keep it minimal.

 

[Ron Roman]

Would that vinegar trick work in the hot water tank to clean out calcium deposits.

 

[Ken Cross]

Aluminum oxide is white and may look like calcium. If the tank is pitted under the deposits, I suspect the deposits are actually the tank itself. Just guessing. If so cleaning with vinegar or any other acid may make the problem worse.
You may be a good candidate for poly tanks.
Ken

 

[Gunni]

Oh ya.. Tanks are aluminum

Hard-water deposits would not be accompanied with pitting and corrosion. What you saw was corrosion damage brought on by sodium hydroxide (bleach), the deposits was the precipitated Aluminum hydroxide created during the alkaline reaction. Aluminum is a poor choice for water storage. You could coat it with a potable water tank product. Typically they are an epoxy compound.

 

[CarlN]

I agree that this is probably from bleach used to clean or chlorine in the water supply reacting with the aluminum.

i would use a different disinfectant (hydrogen peroxide) if needed and use a charcoal filter on the hose to remove chlorine before it gets into the tank.

 

[Mark Maulden]

I went with new aluminum tanks as they are still available from the tank mfgr and I didn't have to modify the supports. I agree they will most likely outlast my remaining sailing career...The boat, according to PO records, has spent all it's life in the Seattle area and points north. Water in this area is from city water from resovoirs fed from snow melt so it's not hard...I should stop at the pool supply for some OTO and see how much chlorine is in it....Maybe I don't want to know

 

[NorthStar]

The corrosion you are getting, white stuff, likely aluminum chloride. Electrolysis is the cause.

 

[NorthStar]

You said you are using CU water lines, copper right? Its electrolysis.

 

[NorthStar]

Google "Fundamentals of Metallic Corrosion in Fresh Water" or "Galvanic Series in Fresh Water." These may help you understand the problem and find a solution.

 

[Mark Maulden]

AAhhh.... Why didn't I think of that? Cu/Al are at opposite ends of the scale. The Cu tubing does goes into a threaded pipe which goes into the tank. Funny the threads in the old Al tank were fine..... I don't know for sure what the pipe is but looks copperish. I think I need to find some red brass or Al to go into the tank and go from there.....But I will do the "googles" and read further. Thanks for the 2X4....It hurt..

 

[Ralph Johnstone]

If It Is Galvanic Corrosion ....................

I think I need to find some red brass or Al to go into the tank and go from there.....

.......................... separate the copper piping from your aluminum tank using a short nylon or poly pipe nipple.

 

[Mark Maulden]

I would. But, usually when I go searching for certain plastic parts, I come away empty handed...... But, it's always an option..