Stored water stays safe by rules, not by luck: the container, the lid, the rotation

Water is not the risky part of storage; the container is. Clean water in a dirty, sunlit, open vessel becomes unsafe on a schedule measured in days, and the household that treats storage like plumbing rather than provisioning is the one that never has to think about this page. The rules are few and physical.

The four conditions

• Food-grade and dark by nature: the blue HDPE drum and the purpose-made storage tank exist because they do not leach and they block light; a translucent container on a sunny terrace is a greenhouse with a tap. The old engine-oil jerry can, however well rinsed, is permanently in the wrong: no scrub reaches the plastic's memory.
• A lid that seals, and a draw that does not need hands: a tap or a pump over a wide open neck. The single most common contamination of stored water is the cup - and the hand that held it, dipped in for the family. One dedicated cup, hanging outside the lid, is a culture war won cheaply.
• Cool, and off the floor: heat multiplies everything biological; a pallet or a stand turns a concrete slab's damp into nothing.
• Rotation as policy: the water you draw first is the water stored first - two drums labelled with their fill dates beat one drum trusted to memory. Week-scale storage wants a weekly top-up from the supply line; month-scale wants a plan (below).

Cleaning the tank that has seen seasons

The honest sequence, doable in a morning with the supply off: drain fully; scrub the walls with a long brush and a detergent solution - biofilm is a film, it comes off mechanically, no disinfectant substitutes for the elbow; rinse until the suds stop; then sanitise - a weak chlorine solution (household bleach, a couple of millilitres per litre of clean water in a standard unscented brand - check your bottle) swished over every surface, or left to stand in a full drum at the same order of dilution, then a short contact time and a thorough rinse. The sediment at the bottom of a borehole-fed tank is a separate page: the same desk's kettle article covers what scale means and when it means the filter order needs attention.

Boil, treat, or test - the line that matters

• Boil: any suspicion after a flood, a cracked lid, an animal's visit - a rolling boil for one full minute and cooling with the lid on is the whole science, the same instruction public-health bodies have given for a century.
• Treat: chlorine tablets designed for water, dosed to the tablet's own instructions, then a 30-minute wait - the correct answer for the long dry-season tank, and a stopgap that never replaces cleaning.
• Test: borehole or well water for the house, once a year, at a real lab - the microbiology and the nitrates are invisible, and this desk will not pretend a page substitutes for a plate count. If the household includes an infant, a pregnancy, or anyone immunocompromised, the clinic's advice outranks every rule of thumb here, including this sentence's neighbours.

One closing habit

Date what you store, cover what you pour, and let the oldest water drink first. The family that does these three things will read this page as obvious - which is the only outcome worth writing about.