Cleaning water tank

kunyang

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I need to flush out the water tank on my new yacht. She has a 100 gallon tank, so I reckon I need 1 gallon of bleach. The trouble is, I can't find the appropriate bleach for the job. I know I need the thin stuff, and should be marked 'suitable for water systems', so where can I get it?

Dave
 

VicS

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I need to flush out the water tank on my new yacht. She has a 100 gallon tank, so I reckon I need 1 gallon of bleach. The trouble is, I can't find the appropriate bleach for the job. I know I need the thin stuff, and should be marked 'suitable for water systems', so where can I get it?

Dave

Unless its very heavily contaminated you wont need that much bleach. Around a litre in a 100 gallon tank should be sufficient......... but drain and rise it out well or the tea will taste foul.

Use supermarket own brand thin bleach. Otherwise about 2.5 litres Milton or equivalent

Subsequently dosing water going into the tank with Milton at the rate of 5ml / 10 litres should keep it sweet.
 
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Momac

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I have about half the size of water tank - 250 litres .
Last spring I used a small (1 litre) bottle of ordinary supermarket own brand sterilising fluid in a full tank of water then left overnight , or a bit longer, with the mixture drawn into the pipes . This made a fairy strong mix and needed at least a couple of full tanks of fresh water pumped through before the chlorine odour was reduced.
This was a precaution in my case - not as a means of dealing with any issue. I think I could have used less of the sterilising product .
.
 

kunyang

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I pick her up on Thursday, and noted that there was a bit of contamination during the survey. I hope I can clear it with a good flush. It's going to take some time to drain down and fill up, but should be worth it, as long as the pump can handle continuous operation for a 100 gallons.
 

ip485

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I use hot tub chlorine granules from any pool hot tub shop or the web.

Cheap, easy to store and mix when needed, and without any other additives.

Are you sure the tank is contaminated and not just the pipes? Its often the pipes and if so just flush these through. Introducing an oxidising agent into metal tanks, assuming they arent plastic or fibreglass, may not be ideal.
 
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EdWingfield

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There is superchlorination, and there is regular dosing thereafter. The first needs active cl at 50ppm to stand in the tank and the plumbing for 24hrs.

On the bleach bottle you will have a manufacturer's tel no. Call them, ask to speak to a technical person. Tell them exactly the situation, and what you propose to do. They will be most helpful.
 
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I normally use bleach, but one advantage of pool chemicals is that the concentration is known, and they give dosing details for shock treatment, but I normally aim for somewhere above 10ppm (10mg per litre) depending on severity.

Taking 250 gallons as about 1000 litres, this means 10g of Cl, or about 250ml of household bleach.
 

jac

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There is superchlorination, and there is regular dosing thereafter. The first needs active cl at 50ppm to stand in the tank and the plumbing for 24hrs.

On the bleach bottle you will have a manufacturer's tel no. Call them, ask to speak to a technical person. Tell them exactly the situation, and what you propose to do. They will be most helpful.

How accurate does this need to be.

Assuming I go to overboard and get 100ppm or even 250 ppm i'm pretty sure it will kill any bugs but is it likely to damage anything usually found in a water system?
Equally if i'm cheap and only get say 30ppm - will it still work, maybe just take longer?

Secondly - if I dose the system up on say a Sunday and leave the boat until the following weekend - is that likely to cause any issues ?
 
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