Water filters: which type to choose for home and for emergencies

The water filter market is full of promises: “living”, “alkaline”, “structured” water. Before buying anything, ask what problem you’re trying to solve: the taste of tap water, well water, or water in an emergency when the mains is off or contaminated. Each has a different answer.

Filter types at a glance

Type	Removes	Doesn’t remove	Power or pressure	For emergencies
Carbon filter jug	Chlorine, taste, odor, some metals	Bacteria, viruses	No	No
Faucet or under-sink carbon filter	Chlorine, sediment, taste	Bacteria, viruses, nitrates	Pressure	No
Reverse osmosis	Almost everything: salts, nitrates, metals, most microbes	Some dissolved gases	Pressure, sometimes power	Only if mains works
Ceramic gravity filter	Bacteria, parasites, sediment	Viruses (most models), salts	No	Yes
Portable filter (straw, bottle, pump)	Bacteria, parasites	Viruses (most), chemicals	No	Yes
UV lamp	Bacteria, viruses, parasites	Chemicals; doesn’t work on cloudy water	Power or batteries	Partly

At home, day to day

Public water supplies in most of Europe and North America are treated and monitored. If the taste of chlorine bothers you, a filter jug or a carbon faucet filter is enough and cheap. Change cartridges as often as the manufacturer says: an old cartridge can itself become a place where bacteria grow.

Reverse osmosis makes sense mainly if you drink well water with nitrates or if old building pipes let rust and sediment through. Downsides: it also removes useful minerals, and for every liter filtered it sends 1 to 3 liters down the drain.

For emergencies

When there’s no mains pressure or power, only gravity and manual filters count:

• A gravity filter usually holds 8 to 12 liters and filters continuously as long as you keep topping it up. Ideal for a family during a long outage or after an earthquake.
• A portable filter fits in the go bag and helps if you have to leave home.

For water that could be contaminated with sewage (after floods, from rivers flowing through towns), combine filtering with boiling or chlorination to deal with viruses too.

What to avoid

• Water ionizers and “alkaline water”: there’s no solid evidence of health benefits, and some devices are very expensive. They do nothing for emergencies.
• Water softeners reduce limescale to protect plumbing and appliances. Useful at home, but they don’t make water safer to drink.
• “Removes 100% of everything” claims. Look for testing to independent standards (such as NSF/ANSI) and read exactly what the filter removes.