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Water Tank Maintenance

My narrowboat has an integral fresh water tank. I have read that these should be painted internally at intervals. But there is no access to the tank at all other than the filler. What can I do to ensure the water remains drinkable and not full of rust?

Asked by: Rod Nelson  | 12.41pm, Monday 6 June

WW says:

Integrated tanks usually have an inspection hatch- quite unusual for there not to be one.
Alas, all you can do is to keep the water disinfected- there is no additive you can use to prevent corrosion in the tank. For this reason, you might want to keep an eye on hull thickness in this region, in case internal corrosion is thinning the hull plating around the tank.
If however, you can gain access to your tank at the sides, it might be worth checking it is truly integral, and not a stainless steel one. However, as you appear to be having rust issues, it does soung like a mild steel tank (or galvanised steel seperate tank, which has started to corrode).
Thankfully, high iron content in the water does not nessicarily make it undrinkable, thought you might consider either a an activated charcoal filter to remove the taste or, combine with a high-level filter (such as the General Ecology range) which then strips out any impurities for the water- and both of these are usually fitted to a dedicated drinking water tap.
The last alternative, though rather drastic, is to get a boatbuilder to cut and fit a waterproof inspection hatch to your tank- which would then allow you to paint the tank internally, or fit a flexible liner is this is a more pragmatic approach. However, depending on the layout, it might not be an easy option to fit a hatch.

Mark Langley  | 3.36PM, Monday 6 June

As Mark says, fitting a flexible liner is not an easy option but it is possible. We did an article called 'A bigger water tank?' October 2007 issue of WW. Although, in this case, it was done to gain a larger water tank, the article describes the basic technique which may be useful to you.

Graham Booth  | 4.28PM, Monday 6 June

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