5 things that help you store water for an emergency in a small space

Standard supermarket water bottles are made from PET plastic rated for single use and a short shelf life — they are fine for drinking that day, less fine for storing under your bed for six months. Food-grade HDPE jerry cans (the blue 10-litre or 20-litre type designed for water storage) are thicker, block more light, and do not leach flavour or degrade the way thin PET does over time. They are also stackable, which matters enormously in a small space. You can often find them secondhand from camping shops or market stalls for a couple of pounds each; new ones are around £8–12 and last years.

You have probably seen one gallon (about 3.8 litres) per person per day repeated everywhere. That figure comes from FEMA guidance that includes cooking, basic hygiene, and a buffer for hot weather or illness. For a temperate-climate flat-dweller planning for a three-day power cut rather than a wildfire evacuation, one litre per person per day for drinking is an honest minimum, with a second litre covering basic cooking and teeth. Knowing the real number keeps you from being put off by an impossible-looking storage target: two people for three days is twelve litres, which fits in a single 10-litre and a 5-litre jerry can under one bed.

Tap water stored in a clean, sealed container does not go bad in the way food does — the issue is that the chlorine added by your water company dissipates over time, leaving the water more vulnerable to contamination from a poorly sealed lid or a container that was not cleaned well enough. The six-month rotation rule is not about the water turning toxic; it is about maintaining a sensible safety margin without making this a monthly chore. Crucially, the act of rotating forces you to actually handle each container — checking it is still sealed, still in a cool spot, and still usable — which is often more valuable than the water swap itself.

This is the one thing on this list you can do in the next three minutes, for free. Frozen water bottles in your freezer serve two jobs at once: they act as thermal mass, keeping the freezer temperature stable longer during a power cut (a full freezer holds its temperature for roughly 48 hours, a half-empty one for about 24, per USDA guidance), and they are last-resort drinking water once they thaw. The common mistake is filling bottles to the brim — water expands as it freezes and will split the bottle or pop the cap, leaving you with a puddle. Fill to about three-quarters, leave the cap slightly loose until frozen solid, then tighten.

Products like the LifeStraw or Sawyer Squeeze are genuinely useful — they filter out bacteria and protozoa from collected water and are cheap, small, and last for hundreds of litres. The mistake is treating a filter straw as your water plan rather than a backstop. Stored clean tap water is easier, faster, and requires no available water source. But if your storage runs out or gets contaminated and you can access a neighbour's water butt, a communal building tank, or intermittent mains supply under a boil notice, a filter straw costs £15–25 and takes up less space than a paperback. It is the one piece of gear that genuinely earns its place in a small flat.