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What's actually in your water

Choose a cartridge for the problem you have rather than for the longest list on the box. Some of these a filter jug solves completely; some it barely touches, and a couple it cannot address at all — which is worth knowing before you spend money on one.

By Maggi Ferguson Founder and editor · Checked August 4, 2026

Limescale and hard water Furred kettles, cloudy tea, white spots on glassware. The most common reason anyone buys a filter jug outside North America. Jugs do this well Chlorine taste and smell The swimming-pool smell. The one thing every filter jug ever made will fix. Jugs do this well Lead Comes from your pipes, not from the water supply. Only some cartridges are certified to reduce it. Jugs do this well PFAS and forever chemicals The contaminant class the whole category is currently reorganising itself around, and the one where the marketing has run ahead of the certification. Some jugs do this Microplastics Mechanical filtration rather than chemistry, so the pore size of the cartridge is what decides it. Some jugs do this Fluoride Almost no gravity jug removes it, whatever you may have read. Two do. Most jugs cannot Bacteria and parasites Outside what a normal filter jug does, and one jug is built specifically to do it. Most jugs cannot Total dissolved solids The number the meter reads, what it does and does not tell you, and the one jug that drives it to zero. Jugs do this well Nitrates An agricultural runoff problem, and largely outside what a carbon jug does. Most jugs cannot Pesticides and herbicides The case where ordinary activated carbon is genuinely good, and certification tells you which cartridges prove it. Some jugs do this Pharmaceutical residues There is a standard for this — NSF/ANSI 401 — and only a few jug cartridges hold it. Some jugs do this Water for tea and coffee Not a contaminant — an extraction problem. And the answer is not the purest water you can make. Some jugs do this

Start with your own water report

Everything on these pages is general. Your water is not. Hardness, lead risk, nitrate levels and whether the supply is fluoridated all vary by street, and every water supplier in the developed world publishes a quality report for your address — free, and usually within two clicks of their homepage.

Read that first. It converts this from a guessing exercise into a shopping decision, and it will often tell you that the thing you were worried about is not present in your supply at all.

One thing it will not tell you is lead, because lead comes from your own pipes rather than the mains. That one needs a sample from your tap, which most suppliers will test on request.