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Water tank treatment

My boat is now three years old and I have a stainless steel water tank, when new I put in the recomended hygiene tablets (can not remeber their name)and have done nothing since, what would you recomend I do for this years boating and future years.We do not drink water from the tank but do wash vegetables with it.

Asked by: David Anderson  | 1.03pm, Sunday 12 February

WW says:

1Boat water systems can often be left for long periods of time without being used. It is important to regularly disinfect the whole system, to prevent excess microbe growth, from the tank to the tap. At least once a year, but possibly more often.
Commercial products are available, but can be expensive to treat the large tanks often found on narrowboats. An alternative is to use very cheap thin bleach (which contains no sodium hydroxide), diluted and added to the tank as it fills.
It must NOT be thick bleach- the cheapest thin bleaches are best.
The solution is then pumped through all taps, shower, and loo connections etc, until a strong smell of chlorine is found. It is then left at least an hour and emptied out (preferably not directly into the canal), followed by refilling the tank and pumping through again. The list below shows the typical dilutions needed- 50ppm (part per million) is sufficient to kill virtually all microbial activity.
You might want to double the concentration for disinfecting hosepipes- and you might want to do this more often.
You can also add chlorine bleach to water to keep the level up as recommended- at 0.5ppm (parts per million)
In October 2009 there was a full article on water systems treatment.
Amount of 5% chlorine (standard thin bleach) to add for:
Volume to treat 50ppm 100ppm 0.5ppm
100 litres 100ml 200ml 1ml
10 litres 10ml 20ml 0.1ml
100 gallons 450ml 900ml 5ml
10 gallons 45ml 90ml 0.5ml

Mark Langley  | 3.29PM, Wednesday 15 February

The table isn't that clear, I am afraid...
100 litres of water needs 100ml of standard thin bleach (or 100 gallons needs 450ml) This will then give a 50ppm solution.
Hope that makes better sense!

Mark Langley  | 3.31PM, Wednesday 15 February

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