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Cleaning water tanks.


sailor0500
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Chlorine bleach (not thick bleach) is what cruise ships use to disinfect the water.  At six-monthly intervals, the entire fresh water system is superchlorinated at a high dose.  Tanks are scrubbed with bleach after maintenance.  It's cheap, simple and it works.  The water in your tank has so little chlorine in it this will have completely dissipated before the tank is empty.  So, I would say that adding some bleach is quite a good idea.  Aim for 1 to 5ppm.  There are resources on the internet to help you calculate the amount to add.

Chlorine attacks stainless steel so don't leave spills on it and don't go too high in the concentration.

Edited by mross
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I think this issue is less relevant to liveaboards  than those of us who mothball our boats in the winter.  Many years ago we lived in a house with a private water supply. Not only did the water travel (from a spring) about half a mile down a cast iron pipe it got stored in a galvanised tank before making its way to the taps.  The supply had to be periodically tested by the local authority and it was always passed safe to drink.  The inspectors said because the water is constantly on the move, as it were, and sealed from light, it doesn't have time for anything nasty to breed within.  I guess it's the same with boats, and more so if you have a relatively small tank so the supply is constantly being replenished with mains water.  Actually there must be thousands of houses that still have piped cold water from a storage tank I doubt many of the occupants worry about disinfecting them periodically.

OTOH I wouldn't dream of drinking water from our boat's tank as it's huge and often sits unattended for weeks on end.  The same applies to the hose pipe we use to fill it.  If you clean your water tank periodically you ought to disinfect your hose pipe as well.  

 

 

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4 minutes ago, mross said:

It's quite easy for bacteria to grow without light but I agree with the rest of your post.

All the water I drink is disinfected with between 3 and 40% alcohol.

All the alcohol I drink is disinfected with between 3 and 40% water in the form of ice.

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I use Elsan Fresh Water Tank Cleaner once a year. Peroxide based, the active ingredient is oxygen, so no effect on people or the environment. Target price is about 8 quid for a half litre bottle. I see little sense in having a fresh water system you don't drink the water from.

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100ml of Elsan Fresh Water Tank Clean for every 20 litres of capacity.  So your half litre will only sterilise 100 litres of fresh water.  You can buy a litre for £7.99.

You can use it to treat your pipework if you dose into a nearly empty tank and run all the outlets for long enough to get the stuff to the taps etc.  But bleach is far cheaper.

Edited by mross
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I just fitted a filter. The water tasted just fine. We had no need for bottled water that's both expensive and space-hogging.

I never buy bottled water at home either, partly for environmental reasons and partly because it's a huge con. Severn Trent go to a lot of trouble to make the water that comes out of my tap at home perfectly safe. 

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That Elsan tank cleaner is not peroxide based at all, the active ingredients seem to be citric acid and bactericides.  It's a more sophisticated product than bleach or peroxide and seems to be marketed as a way of avoiding the "tainting" you can get with oxidisers.  It's possibly a better bet for stainless steel, I guess you could leave it to soak indefinitely , you wouldn't want bleach in your stainless tank for too long.  

I still don't think this is a big deal if you use you water system regularly. If you don't I reckon you either fill containers with fresh water from time to time, not difficult on the cut, or you endure the unpleasantness of "purified" water.  Those high quality expensive filters that claim to filter out everything including bacteria are aimed at yotties that spend long periods away from fresh water sources.  On canals you have a tap every few miles or less where you can get completely safe drinking water - and it's free.

 

    

 

 

  

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26 minutes ago, WotEver said:

I just fitted a filter. The water tasted just fine. We had no need for bottled water that's both expensive and space-hogging.

I never buy bottled water at home either, partly for environmental reasons and partly because it's a huge con. Severn Trent go to a lot of trouble to make the water that comes out of my tap at home perfectly safe. 

I did think of fitting a filter but I remember reading of the crew of a yacht who were all very ill after the filter on the water system was damaged and all the crud in the filter was released into the pipework. I guess nothing is 100% safe. Nice to hear that adding a little bleach as I did on my yachts seems to be a good thing and will probably continue doing that.

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In the caravan where there wasn't really space to fit a filter we used a bit of bleach once a year. Had we been liveaboards on the boat as opposed to occasional leisure users we'd have just drunk it straight out of the tap. 

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the filters can harbour bacteria.  Not likely to be a problem for liveaboards as they are in constant use.

If you are worried about bacteria etc, sterilising once a year is not enough.  Monthly would be better.

Edited by mross
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22 minutes ago, WotEver said:

Nor for occasional leisure users if they're changed as recommended. 

If the recommended change interval is three months, I think the assumption is that they are in almost daily use.  If the boat is unattended for a couple of months I think it would be wiser to put a new filter in.  I'll see if I can get any confirmation.

Here's what Brita say, I'm surprised that it's 100 litres or four weeks!

In order that the quality of your BRITA filtered water is maintained at a high level, you should replace the filter cartridge at regular intervals. 

The service life of the filter cartridge depends on the local water quality: if your mains water contains a carbonate hardness of 12 to 14.5° EH (degree of clarke hardness), then the filter cartridge should be replaced after a consumption of 100 litres of water. If the water is harder or consumption is greater, the lifetime of the cartridge reduces accordingly. 

The cartridge should be replaced after four weeks at the latest, as the requirement for careful hygiene to ensure that you are experiencing optimum performance from your BRITA cartridge.

You don't know the carbonate hardness of your water?

No problem, simply request your free and non-binding BRITA water hardness test strip. It takes just a few seconds to use it to determine if you have soft or hard water. Email your address details to
enquiries@brita.co.uk. 

Important: the test strip can only be dispatched within the UK.

 

Edited by mross
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Brita filters are toys really. They don't operate anything like a 'real' water filter like the Nature Pure. I got involved with manufacturing and selling water filters back in the 80's and there is a huge range of quality generally indicated by the cost of the unit. Brita filters are aimed at domestic consumers who don't really have any need for a quality filter. We have one in our apartment in Gran Canaria, not because the unfiltered water would make us ill (it didn't) but because there's an unusual taste to the water which the Brita removed. 

Nature Pure's filters should be changed either when the flow has slowed appreciably, after 2000 litres, or every two years, whichever comes soonest. 

http://www.purewateronline.co.uk/420400-Nature-Pure-Quick-Change-with-Faucet.html

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Bit of a regular topic this, isn't it. At the end of it all, those who swear by bleach and think 10p's worth once a year is quite enough thank you will continue to use it, same for slightly more extravagant Milton users, there'll be a couple of other proprietary methods, a few whacky ideas, some will drink whatever their tank has to offer and some wouldn't touch it and will continue to buy bottled water whatever. Perhaps someone should have just said "do a search" at the outset! :D

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2 minutes ago, Sea Dog said:

Bit of a regular topic this, isn't it. At the end of it all, those who swear by bleach and think 10p's worth once a year is quite enough thank you will continue to use it, same for slightly more extravagant Milton users, there'll be a couple of other proprietary methods, a few whacky ideas, some will drink whatever their tank has to offer and some wouldn't touch it and will continue to buy bottled water whatever. Perhaps someone should have just said "do a search" at the outset! :D

Well that wouldn't be any fun would it? ;)

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7 minutes ago, WotEver said:

Well that wouldn't be any fun would it? ;)

And, to be fair, I've learned from this thread. I'm gonna be adding Gin henceforth: expensive, but once cut to 3:1 with tonic water it'll go further and I'll be much less inconvenienced by those who overstay on water points! ;)

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5 minutes ago, Sea Dog said:

And, to be fair, I've learned from this thread. I'm gonna be adding Gin henceforth: expensive, but once cut to 3:1 with tonic water it'll go further and I'll be much less inconvenienced by those who overstay on water points! ;)

Perfect :)

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7 hours ago, mross said:

Chlorine bleach (not thick bleach) is what cruise ships use to disinfect the water.  At six-monthly intervals, the entire fresh water system is superchlorinated at a high dose.  Tanks are scrubbed with bleach after maintenance.  It's cheap, simple and it works.  The water in your tank has so little chlorine in it this will have completely dissipated before the tank is empty.  So, I would say that adding some bleach is quite a good idea.  Aim for 1 to 5ppm.  There are resources on the internet to help you calculate the amount to add.

 

That is what we use to use Offshore, a pint and a quarter in 40 tons if I remember correctly, but remember our water came from Gt Yarmouth or Lowerstoft via a hose to a supply ship's tank, slopped around in there for a few days and then pumped onto the platform via another hose that hung out in the elements with the odd dip in the sea when it was rough, so we picked up the odd bug or two that needed killing.

On our boat we do nothing as the water comes straight from the mains to our hose and then to our tank. I make sure the hose is always sealed when not in use and the ends kept clean. I always flush it through before use as well and we treat the water on the boat the same as if we were at home.

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4 hours ago, sailor0500 said:

I did think of fitting a filter but I remember reading of the crew of a yacht who were all very ill after the filter on the water system was damaged and all the crud in the filter was released into the pipework. I guess nothing is 100% safe. Nice to hear that adding a little bleach as I did on my yachts seems to be a good thing and will probably continue doing that.

We tried filters Offshore and found that you could actually get bacteria growing in them if the maintenance was not 100%

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