Foul water

[tangofour]

Help! After returning to the boat after a long absence the freshwater tanks on the boat have gone foul. I mean sewer smellingly bad.

What's the best approach to clean em out an get the water back to fresh and drinkable?

 

[longjohnsilver]

Well I use bleach, about a cup full for 20 gallons, leave it for a few hours and then flush through. White vinegar should get rid of the bleach smell, flush again and hopefully all will be well. If leaving the boat for some time I will add a dribble of bleach to the tank as a preventative measure.

However I do NOT use the tank to drink from, I always keep a seperate container of fresh drinking water.

 

[badman]

I use Milton one cap full each time I top up never had a problem with the water in twenty years sailing.

 

[steviewhitts]

Ditto for both. Use bottled water for drinking and use Miltons fluid for the tank. No problems so far.

 

[Gunfleet]

That's a new one and not what you'd expect. I think I would want to know what was causing it before I used the tank again. Source? Tank? Something ghastly leaking? I'd get a sample tested in a laboratory. When we lived in France and took our water from an underground spring we used to do it regularly and it wasn't too expensive.

 

[KellysEye]

What we do:
- empty tank
- refill with a quarter cup of bleach per 40 gallons
- run some water out of each tap to ensure the bleached water is in every corner of the system
- leave to stand overnight and no more than 24 hours
- empty tank
- refill and empty again
- refill

 

[polwart]

[ QUOTE ]
That's a new one and not what you'd expect. I think I would want to know what was causing it before I used the tank again. Source? Tank? Something ghastly leaking? I'd get a sample tested in a laboratory.

[/ QUOTE ]

Doesn't seem particularly uncommon to me. It happens with water stored on shore for long periods too. Unless of course the suggestion is that it actually is contaminated with sewage - then it will just be the microbial population has proliferated. All water contains some level of bacteria, if it is held stagnant for a long period (particularly if it is warm) then the bacteria (or moulds etc) can grow nicely on any nutrients they can find. The smell is the microbes (or more accurately their metabolites). Some of the worst smelling bacteria will grow in sealed tanks without (or with little air) present.

The previous post gives a detailed process to go through - and I would endorse it (although personally I would use baby bottle sterilising tablets, such as milton or equivalent, at the recommended dosage level - typically 1 tablet for 5 L). What are the tanks made of? Can you see inside them easily. If there is any sludge or debris you want to remove it as it will act as nutrient for the bugs and also reduce the effectiveness of the bleach/biocide you add. If there is a thin layer of slime (biofilm) on the inside of the tanks / pipes etc you really need to get rid of this too. Unfortunately the only really good way to do this is with a scrubbing brush! Next best thing is probably to fill the tank up - add a dribble of washing up liquid and take her out in a force 6!

To avoid it in the future either drain the tanks (and leave them ventilated) before you leave them for a long period OR add a small amount of milton (etc) to the (one tablet for every 25L in your tank) before you go. Keep the tank and filler clean. Check the end of "hoses" are clean/flushed through before filling tanks.

Milton claims to work in 30 minutes, but its worth bearing in mind that this is when used on clean bottles etc that just need sterilised. About 3 hours should be sufficient unless the water is really bad (does in look clean - if you put it in a clear jar/glass?)

Basically all a lab test is going to tell you is you have a problem - which you know! Even if they found something ghastly - they can't tell you if it came in through the filler pipe or a leak.

Finally if you do use tablets - beware most are formulated to "plink fizz" so will give off some gas - make sure the tank is vented.