When to Replace Water Filters
Everything you need to know about the lifespan, warning signs, and replacement timeline for water filters.
The Short Answer
Pitcher and refrigerator water filters should be replaced every 2 to 6 months. Faucet-mount filters last 3 to 6 months. Under-sink and whole-house filters last 6 to 12 months. The activated carbon inside these filters has a finite capacity to absorb contaminants. Once saturated, the filter passes water through without removing anything.
Why Water Filters Need Replacing
Most household water filters use activated carbon (charcoal) to remove chlorine, sediment, volatile organic compounds, and some heavy metals from tap water. Activated carbon works through adsorption: contaminant molecules stick to the carbon's porous surface. Each carbon granule has a finite number of binding sites. Once all sites are occupied, the filter is saturated and contaminants pass through unimpeded.
Worse, a saturated filter can release previously captured contaminants back into the water. Bacterial colonies can also grow on the filter media, especially in warm environments. A filter left in place well past its replacement date may actually make water quality worse than unfiltered tap water.
Reverse osmosis (RO) filters have multiple stages with different lifespans. The sediment pre-filter needs replacement every 6 to 12 months, the carbon filters every 6 to 12 months, and the RO membrane every 2 to 3 years. Neglecting pre-filter changes accelerates membrane degradation, which is the most expensive component.
Warning Signs It's Time to Replace
- The filter indicator light is on (if equipped)
- Water flow has slowed noticeably (filter is clogged)
- Water tastes or smells different than when the filter was fresh
- Chlorine taste or smell has returned
- The filter has been in use past the manufacturer's recommended timeframe
- Visible discoloration or sediment buildup on the filter cartridge
How to Check the Age of Your Water Filters
Most refrigerator and pitcher filters have an indicator light or a manual timer that counts down from the installation date. If your filter does not have an indicator, write the installation date on the filter with a marker. For pitcher filters (Brita, PUR), the manufacturer recommendation is typically every 40 gallons or 2 months, whichever comes first.
Replacement Recommendations
Buy filters in multi-packs for convenience and cost savings. Use only filters certified by NSF International for the specific contaminants you want to remove. NSF 42 certification covers taste and odor (chlorine). NSF 53 covers health-related contaminants (lead, cysts). NSF 401 covers emerging contaminants (pharmaceuticals, pesticides). Check your local water quality report to know which contaminants to target.
The Bottom Line
Replace water filters on the manufacturer's recommended schedule. Pitcher and fridge filters every 2 to 6 months. Faucet-mount every 3 to 6 months. Under-sink and whole-house every 6 to 12 months. A saturated filter provides zero filtration and can harbor bacteria. NSF certification tells you what the filter actually removes.
Frequently Asked Questions
Standard Brita pitcher filters (the white ones) do not remove lead. The Brita Longlast filter and Brita Elite filter are NSF 53 certified for lead reduction. Always check the specific filter model's NSF certifications against the contaminants you want to remove. The packaging and manufacturer's website list which certifications each filter model holds.
In the United States, municipal tap water is regulated by the EPA and must meet Safe Drinking Water Act standards. For most people on municipal water, tap water is safe to drink without a filter. Filters improve taste (by removing chlorine) and can provide an additional layer of protection against contaminants that may be present in your local supply or home plumbing. If you have a private well, regular testing and appropriate filtration are essential.
Sources
- NSF International Water Filter Certification
- EPA Drinking Water Standards
- CDC Water Filtration