Storing and carrying water safely

Water can become contaminated again between source and cup. Most contamination of stored water happens during filling and drawing – through hands, cups, dirty threads or an open lid. That is why safe storage is an integral part of the World Health Organization's multi-barrier principle.

Boiled water or water treated with UV light has no built-in protection: any germ that gets in can multiply. Chlorinated water is somewhat better protected, because residual chlorine keeps making newly introduced germs harmless for a while. But that has limits too.

Light and warmth promote the growth of algae and germs. Cool, dark storage slows these processes. Narrow openings, lids and taps ensure that hands and vessels never touch the water in the first place.

Suitable containers are food-grade, tightly closable ones, ideally with a narrow opening or a tap. In the EU, materials intended for contact with food can often be recognised by the glass-and-fork symbol. Water cans from specialist shops, clean drinks bottles and single-wall stainless-steel bottles are common solutions.

Containers that ever held chemicals, fuel, cleaners or oil are off-limits. Residues cannot be reliably removed, not even by thorough rinsing. Galvanised buckets and plastics of unknown origin are also unsuitable, because they can release substances into the water.

Think about weight as well: one litre of water weighs about one kilogram. A large can quickly becomes too heavy to carry or pour. Several medium-sized containers are often more practical than one huge one and reduce the risk that the whole supply is affected if one becomes contaminated.

Before filling, wash containers with detergent and clean water and rinse thoroughly until no foam or smell remains. Public-health authorities publish instructions for disinfecting containers with a bleach solution – use only their figures, and never mix bleach with other cleaners.

Fill in only treated water, without touching the inside or the threads with your fingers, and close the container immediately. A clean funnel helps you avoid spills. With containers that may be exposed to frost, leave some space: water expands when it freezes and can burst containers.

Label each container with contents and date. That way you know when it needs replacing and you avoid mix-ups. In camp, a colour code helps, for example coloured tape: one colour for raw water, another for drinking water.

Store water cool, dark and away from chemicals, fuels and strong-smelling substances. Some plastics can absorb odours from their surroundings. Direct sun warms the water and promotes algae and microbial growth.

Replace self-filled stocks as recommended by your public authority; the intervals differ between authorities and depending on how the water was treated. Bought bottled water keeps until its best-before date if it is sealed and stored properly. If you regularly use up stocks and buy more, you always have fresh water in the house.

For quantity, the BBK gives around two litres per person per day as a planning figure for emergency preparedness, plus a reserve for heat, children, sick people and pets. If space allows, plan extra water for hygiene.

Never use containers that held chemicals, fuel or cleaners. This is the most important rule – poisoning from residues cannot be fixed by any water treatment.

Do not dip hands or cups into the supply. Draw water through a tap or by pouring it into a clean vessel. Keep raw-water and drinking-water containers strictly separate and clearly marked so they cannot be mixed up.

Open buckets, barrels and tubs of water can be a drowning hazard for small children. Cover them and keep them out of reach. And remember: storage does not make unsafe water safe. Only treated water belongs in the drinking-water supply.