Cleaning/Sterilising Water Tanks

[jimbaerselman]

Couple of things:

(1) You can get rid of chlorine residual smell with a much diluted acid - some vinegar in a water flush does fine. VicS would know the chemistry.
(2) If light gets into your storage (transparent pipes, translucent tanks moulded into the hull) you'll get algae growth. Use light-proof piping! And Vyv's toilet brush in the tank.

Fairly comprehensive story: http://www.jimbsail.info/going-foreign/boat-prep/pure-water, written because we learnt the hard way, running charter fleets, and this query comes up every year . . .

 

[Mistroma]

When I used a similar method on our tank it was not 100% successful. I needed to flush the tank several times to get rid of the chlorine smell and taste, so it isn't a method I would advocate for them. Probably worth trying for hoses but mine were 25 years old and deteriorating on the outside(!), so well past their sell-by date.

Vyv, the vent pipe was only 5 years old and in perfect condition, not surprised that bleach wouldn't completely clear surface of 25 year old pipes.

N.B. See my earlier post about getting rid of chlorine smell after using bleach. The reaction is very quick and extremely well known by chemists. Many chemical plant workers (dye & pigment industry) used to use it daily when cleaning hands at end of a shift. Dunk hands in hypochlorite solution, rub together, dunk hands in metabisulphite solution before rinsing. Voila clean hands & no smell. A bit extreme but it worked well and didn't seem to cause skin problems (but they were a tough lot and used to it).

So sodium hypochlorite solution kills off bleach, no smell left from bleach. Sulfite smell (and taste) will be left but much is easier to remove than smell from bleach. Sulfite readily oxidises to sulphate and you won't taste that even without rinsing. Little flushing required, I find one rinse is fine after dissolving some metabisulphite and sloshing it around.

I see Jim suggesting use of vinegar. It works to drive out residual chlorine but then you have residual vinegar and can taste that. However, it is another solution to the problem and works well. The human palate is pretty well insensitive to sulphate but sensitive to tiny amounts of sulphite. So very dilute sulphite solution will become tasteless fairly quickly with a little agitation and oxygen (i.e. Normal filling process from a hose).

 

[Spirit of Glenans]

2nd that - Puriclean.

Had a very foul flexible v-berth poly tank. Tried everything, including bleach to clear it. It was out of the boat and really black. Puriclean worked a treat.

If you only really use tank water for cooking washing etc - add a couple of tsp of sodium Metabisulphate every time you refill. Not great for tea or coffee - but I never use tank water for that anyway. Faint smell of sulphur - but squeeky clean tank all the time

This is the stuff recommended for home-brew equipment.

 

[VicS]

This is the stuff recommended for home-brew equipment.

Sodium metabisulphite ? Yes!

 

[Momac]

We don't drink tank water but carry a container which we refill from the mains tap - which is not an issue for us.

I did use Milton in our tank last summer but it was a new to me boat and unknown idle period before that. After a good long soak it took two full tanks flushed through to clear the aroma of the Milton.

The water is presently drained off for the winter.

I don't intend to repeat the Milton treatment but will flush a whole tankful of fresh water through in the spring.
I did this with our last boat over 6 years with no issues (in the UK).

But in a hot climate I imagine it is wise to be more careful.

 

[JumbleDuck]

I use Puriclean every few years, just in case. I find it needs at least three and preferably four complete flushes, and even then the first tank of water makes my lips go numb for a bit. Doesn't seem to have any other ill effects.