You turn on the tap and the water tastes off. You think about getting a filter. You go online and find hundreds of options: pitchers, faucet-mounted filters, under-sink systems, reverse osmosis. They all promise pure, safe water. But do they actually work? And which one should you choose?

Water filters aren't all created equal. Some only improve taste. Others remove dangerous contaminants. Still others strip out the good minerals too. Choosing the wrong one means wasting money or, worse, drinking less safe water.

Different types of filters

Pitcher filters are the most common. They're cheap (€20–40), convenient, and ready to use right away. They contain activated carbon filters and ion-exchange resins. They remove chlorine, improve taste, and reduce limescale. But they don't purify against bacteria or serious contaminants.

Faucet-mounted filters screw directly onto your tap. They cost €30–60. They filter water as it flows. More effective than pitchers for volume, but slower. They remove chlorine, sediment, and some heavy metals. They don't remove everything.

Under-sink systems are installed beneath the sink. They cost €200–500 plus installation. They filter all the water you use in the kitchen. They have larger, more powerful filters. They remove a wider range of contaminants.

Reverse osmosis systems are the most powerful. They cost €300–1,000. They remove almost everything: bacteria, viruses, heavy metals, pesticides, pharmaceuticals. But they also remove good minerals. The water becomes pure H2O, almost distilled.

What they actually remove

Chlorine: all filters remove it. It's easy to filter with activated carbon. If your only problem is chlorine taste, a cheap pitcher is enough.

Limescale: pitchers and some filters reduce limescale (calcium carbonate). But they don't eliminate it. If you have very hard water, you need a water softener, not just a simple filter.

Heavy metals (lead, copper, mercury): quality activated carbon filters reduce them. Reverse osmosis systems eliminate them completely. Budget pitchers aren't sufficient.

Bacteria and viruses: only filters with ultra-thin membranes or UV systems remove them. Pitchers and standard filters don't protect against bacteria. If your water is microbiologically contaminated, you need boiling or specialized systems.

Pesticides and pharmaceuticals: only reverse osmosis and some super-activated carbon filters remove them effectively. Basic filters aren't enough.

When you really need a filter

If your tap water has a strong chlorine taste: a basic pitcher or faucet filter solves it. No need to spend much.

If you live in an area with hard water (lots of limescale): an anti-limescale filter or softener improves appliances and your boiler. But for drinking, limescale isn't dangerous.

If your building has old pipes and you're worried about lead or copper: an under-sink filter with quality activated carbon is good protection.

If your tap water is contaminated (bacteria, agricultural pollutants): you need reverse osmosis or an advanced purification system. But in Italy, it's rare for tap water to be that contaminated. Check local water quality reports first.

When a filter is useless or harmful

If your tap water is already good and safe: the filter removes chlorine but also useful minerals. The water becomes "empty." It's not always an improvement.

If you don't change the filter regularly: an old filter is worse than no filter. Bacteria multiply in a saturated filter, and the filtered water becomes more contaminated than the original.

If you use reverse osmosis without remineralization: water that's too pure can be corrosive to pipes and lacking in minerals for your body. You need a post-filter that remineralizes.

The maintenance problem

Every filter has a lifespan. Pitcher cartridges last 4–6 weeks or 100–150 liters. Faucet filters last 3–6 months. Under-sink filters last 6–12 months. Reverse osmosis filters last 1–3 years.

If you don't respect these timelines, the filter becomes saturated. It stops filtering, or worse, releases what it's accumulated. The cost of replacements should be factored into your initial investment.

A pitcher that costs €25 seems cheap. But filters cost €5–8 and last a month. That's €60–96 a year. Over 3 years, you've spent €200–300. An under-sink system with annual replacements might cost less in the long run.

How to choose the right filter

First: analyze your tap water. Ask your local water authority for the data or get a private analysis done (costs €80–150). This way you know what's in it and what you want to remove.

Second: define your goal. Do you just want to improve taste? Do you want protection from heavy metals? Do you want total purification? Each goal has its own solution.

Third: calculate the total cost over 3 years. Initial price + replacement cost × 3 years. Often a more expensive system initially costs less long-term.

Fourth: choose certified brands. Filters must meet European standards (EN) and have NSF certifications. Be wary of filters without certifications.

Important certifications

NSF/ANSI 42: reduction of chlorine, taste, odor. The minimum standard for any filter.

NSF/ANSI 53: reduction of health-related contaminants (lead, cysts, some pesticides). This is important if you want real protection.

NSF/ANSI 58: reverse osmosis systems. Check that they remove at least 90% of declared contaminants.

If a filter has no certification, it's just a tube with carbon inside. It might do nothing.

Alternatives to filters

Boiling water: kills bacteria and viruses, but doesn't remove metals or chemicals. Useful in emergencies, not as a permanent solution.

Bottled water: seems simple, but costs a lot over time and creates plastic waste. If your tap water is good, a cheap filter is more sustainable.

UV purifiers: use ultraviolet light to kill bacteria and viruses without removing minerals. Great if the problem is microbiological, useless for metals or chemicals.

Get your tap water tested

Before buying any filter, find out what's in your water. Search online for your local water authority's analysis. It's usually published on your municipality's website or your local health authority's site.

If you want specific data for your home, call an accredited lab. They'll send a technician, take a sample, and give you results in a week. It costs €80–150 but saves you from buying useless filters.

Choose based on results

Good water with just chlorine taste: a pitcher filter for €25–40. Done.

Water with traces of lead or copper (old building): an under-sink filter with quality activated carbon (€200–300).

Water with agricultural or industrial pollutants: reverse osmosis with remineralization (€400–800).

Don't buy reverse osmosis if you only have chlorine. That's like using a cannon to kill a fly.

Set reminders for filter changes

Set a phone reminder. Pitcher: every 4 weeks. Faucet filter: every 3 months. Under-sink: every 6–12 months. Reverse osmosis: check each filter according to the manual (they vary).

Write the installation date on the filter label. That way when the reminder comes up, you know exactly how old it is.

Don't believe exaggerated claims

If a filter promises to "alkalize," "structure," or "energize" water: stay away. These are meaningless marketing terms, not real benefits.

If it promises to remove "all toxins" for €39: it's impossible. Effective filters cost money. If the price seems too good to be true, it probably doesn't work.

Test before buying expensive systems

If you're considering a €500+ system, ask for a trial period. Reputable companies offer them. Test for 2–4 weeks, see if the water really improves, then decide.

Read independent reviews (not those on the manufacturer's site). Look for independent lab tests, not customer testimonials.

Clean your pitcher regularly

If you use a pitcher filter: wash it every 3–4 days. Stagnant water, warmth, bacteria—it all promotes microbial growth. A dirty pitcher makes water worse, not better.

Wash with hot water and vinegar. Rinse well. Dry completely. Never leave stagnant water in the pitcher for days.

For reverse osmosis: remineralize

If you buy a reverse osmosis system, make sure it has a final remineralizing filter. Water that's too pure isn't good to drink long-term. Your body needs minerals.

If your system doesn't have one, you can add a pinch of Himalayan salt per liter (literally a pinch). It slightly remineralizes the water without changing the taste much.

Consider environmental impact

A filter that keeps you from buying 100 plastic bottles a month is a green choice. But if the filter itself uses lots of plastic in replacements, the impact shrinks.

Look for filters with recyclable replacements or low impact. Some brands have recovery programs for used filters. That's a plus to consider.