cleaning water/deisel tanks

[morays]

Hi,

I have some discoloration in my water from my water tanks. This is the first time I have had this in 2 years and I liveaboard so the water is constantly being replenished. I am not sure if there was something in the mains water upstream of the boat when I last filled it (doubtful) but I need to get the tanks cleaned. I will drain the water out and refill tonight but I wanted to know what I could do to get the tanks cleaned either myself or through a 3rd party.
All three of the tanks on my Caliber 40 are made of aluminum. The PO fitted 10 inch removable covers on the top of all three tanks but there is no viewing window so I will have to unscrew all covers and replace the gaskets once finished. I dont even know if the tanks will be fitted with baffles.
Can I use a "purification" product to ensure the water is contaminant free in the future? Should I shock the tanks with bleach? I read on another forum that this can leave crystals in the tank which will be corrosive to the aluminum if left for long. If this is the case what concentration would be safe to use and how long should I leave it in the tank for? Can I run the water pump to drain the tank or will the bleach damage the pump seals? Any help would be greatly appreciated.

Moray Sandison
s/v Sol Purpose

[marshmat]

Let's take a look inside the tanks before trying to figure out which chemicals to pour in there. The odds are they'll need scrubbing no matter what, and hopefully whatever you find can be cleaned up without too many chemicals.

If what you find in the tanks is brown and slimy, the solution might be different than if you find green and slimy, or brown and powdery, or white and crystalline, etc. (A point-and-shoot camera should fit in there with the tanks drained, if you want to share what you find.)

You say you'll have to replace the inspection port gaskets if you open them? That's OK. You'll need to add spare gaskets to your parts inventory anyway. And now you'll know what to expect.

[Cavalier]

Originally Posted by morays

Hi,

I have some discoloration in my water from my water tanks. This is the first time I have had this in 2 years and I liveaboard so the water is constantly being replenished. I am not sure if there was something in the mains water upstream of the boat when I last filled it (doubtful) but I need to get the tanks cleaned. I will drain the water out and refill tonight but I wanted to know what I could do to get the tanks cleaned either myself or through a 3rd party.
All three of the tanks on my Caliber 40 are made of aluminum. The PO fitted 10 inch removable covers on the top of all three tanks but there is no viewing window so I will have to unscrew all covers and replace the gaskets once finished. I dont even know if the tanks will be fitted with baffles.
Can I use a "purification" product to ensure the water is contaminant free in the future? Should I shock the tanks with bleach? I read on another forum that this can leave crystals in the tank which will be corrosive to the aluminum if left for long. If this is the case what concentration would be safe to use and how long should I leave it in the tank for? Can I run the water pump to drain the tank or will the bleach damage the pump seals? Any help would be greatly appreciated.

Moray Sandison
s/v Sol Purpose

Hi Moray,

Welcome to CF!

Are you tanks baffled, i.e. do they have internal walls to stop the water sloshing about?

If the problem has suddenly appeared overnight then it's unlikely that it is long-term corrosion, but may be a short term problem caused by a contaminant introduced inadvertantly into the tank.

Does the discolored water come out of every faucet or just one? i.e. have you checked to ensure it is the tank and not the water heater or one of the faucet's valves which are corroded?

I would definitely dump the contents of the tank - but not straight away. As before you do this you'll, have a good opportunity to discover what the problem is. If you dump the water and replace it - and electrolyte or contaminant which was in the water may take a while to present itself again i.e. you may run with clean 'looking' water for a while only for the problem to show itself later.

If you take a trip to Home depot the have the following piece of kit:
Small Pool/Spa Jet Vacuum-68008 at The Home Depot
..it's cheap and all you'll need is that and a water hose. There's a return line hose which you can either dump over the side or dump over the side into a bucket. It comes with a mesh-bag so that you can catch whatever the venturi picks up.
You have 10" accesses so the 7" head will fit in - don't bother with a pole.. if you only have the hose attached then you can rummage around with the venturi head (which has brushes on it too) to find out what's in the bottom of the tank: You could have had dirt, rusting fine swarf or anything appear in the tanks so it's worth trying to find out what it is first. If you end up with white-grey goop on the brushes you may have a short-term corrosion problem caused by the introduction of a contiminant into the tank.

Once you've done that i'd dump the tank, borrow a non-high power pressure washer and spray directly into the tank though the access hatches (in combination with a good stiff brush) and try to displace as much of the contaminants off the inside of the tank as possible.
Once that's done, you can dump the content again and then fill the tank with fresh water.
I'd avoid putting any form of shock treatment in there, especially chlorine-based ones. You have no idea how the chlorine will react to the aluminium when it's electrically connected to other fittings. The last thing you want is perished gaskets and pumps eroded.
Your best bet is something like Dettol:
dettol in usa - BuyCheapr.com
..it's basically what's used as a strong liquid disinfectant (you can even use it on baby-feeding equipment). I'd empty a whole bottle into a full tank of water and agitate it. Dettol's is exceptionally good as removing mildew-type moulds and organic slimes. Leave this overnight and dump the tank in the morning - it's mild enough to not cause problems diluted in the marine environment, but you should find a drain for it (even if this means carrying a bucket at a time).

Two more flushes through with a fresh water source should get you to the place of being able to refill the tank for good.

Good luck!

Phil