Sanitise water system after 4 years out of service.

wipe_out

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Hi,
Previous owner put the boat out of commission in 2015 and now we are trying to get it all in order.. Now thinking about the water system..
Any suggestions how to rinse, clean, sanitise and recommission the water tank and water system as a whole?
 

rotrax

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Hi,
Previous owner put the boat out of commission in 2015 and now we are trying to get it all in order.. Now thinking about the water system..
Any suggestions how to rinse, clean, sanitise and recommission the water tank and water system as a whole?

I carried this out on our new boat three years ago.

I used a 2 litre thin bleach, supermarket own brand. I quarter filled each tank-we have 2 200 litre tanks-put in a litre of bleach in each tank and filled both full to overflowing out of the breathers. Each tap/outlet was opened wide until plenty had flowed through, then shut off. I left it to stand four days, pumped it all out, refilled, pumped it all out and then started using the tank water. Very slight clorine taste for the first two fills, then it was gone.

We use Milton or pound shop sterilising liquid at each refill. Just a splash.

The boat had been left four almost five years with half full tanks before we got her and all outlets were quite smelly.

Been good since we carried out the above. Every lay-up I drain the tanks, re-fill, pump out and re-fill. We drink the water happily and with no ill effects.
 

pvb

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Yes, ordinary own-brand supermarket thin bleach is fine. Once clean, you can also use a tiny dose of the same bleach to treat each new refill (Milton and cheap sterilising liquids are bleach-based). Or you can use water purification tablets. I use Aqua Midi tablets, by Clean Tabs - https://www.cleantabs.co.uk/midi-tabs.php - and the water is fine.
 

Mistroma

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Yes, ordinary own-brand supermarket thin bleach is fine. Once clean, you can also use a tiny dose of the same bleach to treat each new refill (Milton and cheap sterilising liquids are bleach-based). Or you can use water purification tablets. I use Aqua Midi tablets, by Clean Tabs - https://www.cleantabs.co.uk/midi-tabs.php - and the water is fine.

Yes, I'd use bleach without thickeners. No need to worry about a lot of rinsing, just add a solution of Sodium metabisulfite when refilling. It will kill off all the bleach immediately. You would get an aftertaste because the human palate can detect a few parts per million of excess SO2. Fortunately, SO2 will convert to sulfate very rapidly. Just filling a tank mixes in water with sufficient oxygen to remove the SO2.

Humans can't readily taste sulfate, even at quite high concentrations.

I remember using this fact years ago when presented with a bottle of undrinkable white. The waiter tasted it, admitted someone had overdone addition of sulfite and brought another bottle. I asked for 2 jugs, poured the tainted wine back and forth a couple of times and offered some to the waiter. He was rather surprised to find it was now drinkable and actually not too bad.
 

VicS

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Hi,
Previous owner put the boat out of commission in 2015 and now we are trying to get it all in order.. Now thinking about the water system..
Any suggestions how to rinse, clean, sanitise and recommission the water tank and water system as a whole?

Use thin domestic bleach at the rate of 25cm³ per 10 litres of water for sanitising the tanks and pipework if you think it is necessary

Treat the water in the tank with Milton at the rate of 5 cm³ per 10 litres . Once or twice a year should be adequate unless you fill from a suspect source, then treat all the water at this rate.

If using thin bleach to treat the water use at the rate of 2 cm³ per 10 litres, but remember bleach may contain substances you may prefer not to drink.

(Dont exceed the does rate for the water or you will have lousy tasting tea , unless you have a filter which takes out the chlorine)
 

simonfraser

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you might want the check the filters / tap ends too.
after all those years could be quite a bit of grit in, especially when you start rinsing and agitating.
 

VicS

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Use thin domestic bleach at the rate of 25cm³ per 10 litres of water for sanitising the tanks and pipework if you think it is necessary

Treat the water in the tank with Milton at the rate of 5 cm³ per 10 litres . Once or twice a year should be adequate unless you fill from a suspect source, then treat all the water at this rate.

If using thin bleach to treat the water use at the rate of 2 cm³ per 10 litres, but remember bleach may contain substances you may prefer not to drink.

(Dont exceed the does rate for the water or you will have lousy tasting tea , unless you have a filter which takes out the chlorine)

For a tank which has been unused for several years Peggie Hall recommends

1. Prepare a chlorine solution using one gallon of water and 1/2 cup (4
oz) Clorox or Purex household bleach (5-7% sodium Hypochlorine
solution). With tank empty, pour chlorine solution into tank. Use one
gallon of solution for each 5 gallons of tank capacity.

2. Complete filling of tank with fresh water. Open each faucet and drain
cock until air has been released and the entire system is filled. Do
not turn off the pump; it must remain on to keep the system pressurized
and the solution in the lines.

3. Allow to stand for at least three hours, but no longer than 24 hours.

4 Drain through every faucet on the boat (and if you haven't done this
in a while, it's a good idea to remove any diffusion screens from the
faucets, because what's likely to come out will clog them). Fill the
tank again with fresh water only, drain again through every faucet on
the boat.

5. To remove excess chlorine taste or odor which might remain, prepare a
solution of one quart white vinegar to five gallons water and allow this
solution to agitate in tank for several days by vehicle motion.

6. Drain tank again through every faucet, and flush the lines again by
fill the tank 1/4-1/2 full and again flushing with potable water.
 

JumbleDuck

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Perhaps the OP is afraid of finding some legionnaires in there.

Could be. My last boat sat in a boatyard for six (iirc) years and at the end of it the water in her flexible tank was perfectly drinkable. Or at least it smelled fine, it tasted fine and I drank it with no ill effects. My current boat also has flexible tanks, about which I don't worry as much as if there was an air space above the water.
 

VicS

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I'm a bit confused with the dosages here. Wouldn't it be easier to say dilute to between 1:200 and 1:400 ?

Peggie's words, not mine!

ITYWF that her figures work out at a dilution of 160. ( remember a US gall is smaller than a UK gallon) They are based on a US code of practice for cleaning tanks in RVs and boats

My figures for Milton are what they recommended for sterilizing tanks and containers for caravanning and camping. My suggestion of 2cm³ thin bleach per 10 litres may be rather high. I do not remember where that came from
 
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vyv_cox

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Having owned our 35 year old boat for the past 25, I found that although the water tasted half reasonable we thought it could be better, despite regular dosing with Milton. I removed the inspection hatch on the tank and found a lot of black, mould-like deposits. I was only able to reach one end of the tank with a brush to scrub it all off (a new toilet brush on a stick is very effective) so I cut a second inspection hatch. The resulting improvement in water taste was rewarding but the biggest improvement came when I replaced the hoses. The outside of these was unpleasantly sticky and the inside was black. Adding a General Ecology filter was the final icing on the cake.
 

geem

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Having owned our 35 year old boat for the past 25, I found that although the water tasted half reasonable we thought it could be better, despite regular dosing with Milton. I removed the inspection hatch on the tank and found a lot of black, mould-like deposits. I was only able to reach one end of the tank with a brush to scrub it all off (a new toilet brush on a stick is very effective) so I cut a second inspection hatch. The resulting improvement in water taste was rewarding but the biggest improvement came when I replaced the hoses. The outside of these was unpleasantly sticky and the inside was black. Adding a General Ecology filter was the final icing on the cake.

We cleaned our tank this year. We fortunately have two very big access lids so we can get in the tank. We also had a black mold like growth. We use a pair of standard 10” filter units. The first has a 1 micron filter the second a carbon filter. The 1 micron protecs the carbon filter from debris so increases the life of the carbon filter. We were getting muck in the 1 micron filter to decided to do the tank clean.
Now the tank is nice and clean and only ever filled with water from our water maker, the 1 micron filter is nice and clean.
We used a product called VWP. It is used for sterilising home brew kits etc. Its cheap and effective. We added some to the part filled tank and pumped it through the pipes to the sink and wash hand basins. It was suprising how much muck came out of the pipes! Once we had used the VWP we rinsed the tank and pipes again with sodium metabisulphate to neutralise the chlorine in the VWP. Re installing the filters we are back to good tasting water and a very clean and sterile tank.
 
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