How does a water filter work and what types of filters are there?
A home water filter traps substances as water passes through it. The CDC says filters remove substances based on pore size, the size of the substance and its electric charge. Types range from pitcher and fridge filters, which mostly use activated carbon for taste and smell, to reverse osmosis, which also removes germs and some chemicals.
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How does a water filter work?
A filter holds back substances that are too large to pass through its pores, and some designs also act on a substance’s electric charge. The CDC notes that filters can also remove helpful substances, such as chlorine and fluoride.
What types of water filters are there?
By where they sit in the home:
- Pitcher and fridge filters: usually activated carbon, used to improve taste and smell. The CDC states that most of them are not designed to remove germs.
- Faucet-mounted and under-sink filters: treat water in batches at one tap, such as the kitchen sink.
- Whole-home filters: treat all water entering the house. If one removes disinfectant, germs may grow more easily in the plumbing.
By how fine the filter is, the CDC lists four tiers:
- Microfiltration: removes parasites such as Giardia and Cryptosporidium and is somewhat effective on bacteria, but does not remove viruses or chemicals such as lead.
- Ultrafiltration: removes parasites and bacteria and is somewhat effective on viruses.
- Nanofiltration: removes parasites, bacteria and viruses, and some chemicals.
- Reverse osmosis: removes germs and some chemicals, including lead, copper, chromium, chloride and sodium.
What other home treatments exist?
The CDC also lists distillation (boiling water and collecting the steam), ultraviolet light, which treats germs but not chemicals, and water softeners, which remove minerals such as calcium and magnesium.
How do I pick one?
Check the label for NSF certification: Standard 42 covers taste and odor, 53 cyst reduction and 58 reverse osmosis. For parasites, the CDC advises an absolute pore size of 1 micron or smaller; for bacteria, 0.3 micron or smaller. Change filters on the manufacturer’s schedule.
People also ask
Do pitcher water filters remove germs?
According to the CDC, most home water filters such as pitcher or fridge filters are not designed to remove germs. They typically use activated carbon to improve taste and smell and may reduce some metals such as lead.
What does reverse osmosis remove?
The CDC says reverse osmosis removes parasites, bacteria and viruses, plus some chemicals including lead, copper, chromium, chloride and sodium. The system label lists the specific chemicals it removes.
What does an absolute pore size mean on a filter?
An absolute rating sets a maximum pore size, so anything larger is caught. A nominal or mean rating gives only an average, so some larger particles may pass through (CDC).
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