How long does a pitcher filter last?
As long as a filter is kept in a cool dry place, it will last indefinitely. Once a filter touches water, its efficiency will drop off significantly once it has filtered 100 gallons or once it has been 6 months, whichever comes first. If your tap water is heavily contaminated (most likely if you live in a large or older city), your filter must work harder to keep your water clean, which will decrease the life of the filter.
People drink water at different rates, so they reach the 100 gallon mark at different times. Here is our recommended timetable for replacing your filter:
Families: 2–3 months
Couples: 3–4 months
Individuals: 4–6 months
If you'd like to run the calculations yourself, you will want to measure how long it will take you to filter 100 gallons of water. The top reservoir is ½ gallon when completely full, so you can fill it 200 times before you need to change it.
For example, if you fill your top reservoir twice a day, you'll filter 100 gallons in 100 days, or around 3 months.