When Should I Replace My Water Filter?
Divide your filter's rated gallons by the gallons you filter each day. A 1,000-gallon filter used at 2 gallons a day lasts 500 days, about 16 months. Enter your filter's rating and daily use below to get a replacement date and a calendar reminder.
How it works
The formula is days = rated gallons / gallons per day. The tool adds that many days to your install date. If you enter a maximum number of months from the filter label, it uses whichever limit comes first, because many filters have both a volume rating and a time limit.
The only Dr. Water filter rating in our product data is the Hydrogen Water RO Machine filter, listed on its product page as "up to 1,000 gallons (4,000 liters)". For any other filter, read the rating on its package and choose "Other filter". A typical home uses a few gallons a day for drinking and cooking, but your own number is better than a guess.
Sources
Reference information only. Not medical advice. Last reviewed 2026-10-30.
Frequently asked questions
How often should I replace a water filter?
Follow the label on your filter. Most filters have a volume rating in gallons, a time limit in months, or both. Replace at whichever limit comes first.
How do I calculate how long a filter lasts?
Divide the rated gallons by the gallons you filter each day. A 1,000-gallon filter at 2 gallons a day lasts 500 days.
How long does the Dr. Water RO Machine filter last?
The product page lists the filter for up to 1,000 gallons (4,000 liters). Your time depends on how much water you filter each day.
What are signs a filter needs replacing sooner?
Slower flow, a change in taste and a change in smell can all mean a filter is used up. Replace it when you see them.
Does the calendar file work on my phone?
The .ics file opens in Apple Calendar, Google Calendar and Outlook. Open the downloaded file and add the event.
A countertop machine that filters water. The product page rates its filter for up to 1,000 gallons.
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