Author Topic: [UPDATED] Protection from Bacteria in Water Tanks and Shower Heads  (Read 6022 times)


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  • Old Salt
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    • Dolcetto - My Boat
When did you last disinfect your shower head or sanitise your water tanks?

I recently started discussions on YBW regarding disinfecting your shower head and sanitising your water tanks. If you think you are immune from problems, this is what prompted the first thread: "As some of you may know, I've been in hospital with pneumonia ..." It is possible that a Legionella infection occurred from the shower head on my boat.

The YBW thread diverged into disinfection of water tanks, which was also useful. I had previously used Milton tablets for this, but I have found a cheaper and more powerful alternative. I have bought some "mini" stabilised chlorine tablets. They are about the diameter of a pound coin, and twice the thickness, so will easily drop into the water tanks.

The tablets are Sodium Dichloroisocyanurate Dihydrate (NaDCC), rather than Sodium Hypochlorite (in bleach). The Wikipedia article says "... As a disinfectant, it is used to sterilize drinking water, swimming pools, tableware and air, fight against infectious diseases as routine disinfection...".

One tablet will raise the free chlorine level by 1ppm (1mg/l) in 1000 litres of water (Note: 50% higher dose tablets now available). For my 240 and 350 litre tanks two tablets are ideal for an initial shock dose (6 to 8ppm), but too strong for potable use where 0.5 to 1ppm is more appropriate. I generally drink bottled water (as it is cold), but use tap water for coffee. I will use the bottled water for all consumption until the shock dose has weakened, adding ½ or 1 tablet at each full refill.

NaDCC tablets on Amazon
NEW 50% Higher Dose NaDCC tablets on Amazon

Uses and Effectiveness of NaDCC
NaDCC Material Safety Data Sheet (MSDS)

Other potable water purification tablets use NaDCC, so providing the dose is about right there should be no problems, see below.

Oasis water purification tablets contain NaDCC.
Dosage: one 167mg tablet per 20-25 litres, cost 10p from eBay.
Mini NaDCC tablets are 3.2g (20x 167mg) so should be OK for 400 litres at the same potable dose, cost 5p.

Aqua Clean Tabs also contain NaDCC.
MSDS for Clean Tabs products here.

More dosage information for potable water at WHO Food Additives
Nigel Mercier: Forum Administrator