How Often Should You Replace Water Filters?
Pitcher: every 2 months. Under-sink: every 6 months. RO membrane: every 2-4 years. Here is the complete schedule by filter type.
Complete Replacement Schedule by Filter Type
| Filter Type | Replacement Interval | Gallon Rating | Annual Cost |
|---|---|---|---|
| Pitcher filter (Brita Elite) | Every 2 months | 120 gallons | $40–$60/year |
| Pitcher filter (Clearly Filtered) | Every 4 months | 100 gallons | $75–$90/year |
| Faucet mount (Brita, PUR) | Every 3 months | 100–200 gallons | $30–$50/year |
| Refrigerator filter | Every 6 months | 200–300 gallons | $50–$150/year |
| Countertop RO (AquaTru) | 3–12 months by stage | Varies by stage | $100–$130/year |
| Under-sink carbon (Aquasana AQ-5300+) | Every 6 months | 500 gallons | $100/year |
| Under-sink RO — sediment stage | Every 6–12 months | 3,000–5,000 gallons | $10–$20/change |
| Under-sink RO — carbon pre-filter | Every 6–12 months | 3,000–5,000 gallons | $12–$25/change |
| Under-sink RO — membrane | Every 2–3 years | 10,000–20,000 gallons | $30–$60 every 2-3 years |
| Under-sink RO — post-carbon | Every 12 months | 5,000 gallons | $12–$20/year |
| Whole-house sediment pre-filter | Every 3–6 months | Varies by turbidity | $15–$30/change |
| Whole-house carbon block | Every 6–12 months | 50,000–100,000 gallons | $40–$80/change |
| Whole-house KDF media | Every 12–18 months | Varies | $60–$100/change |
| UV lamp (Viqua D4) | Every 12 months | Time-based only | $60–$90/year |
| Water softener resin | Every 10–15 years | N/A | $150–$300 when needed |
Signs Your Filter Is Exhausted (Before It Fails Silently)
Carbon filters (under-sink, pitcher, whole-house)
Signs: Return of chlorine smell or taste; water starts smelling like your tap water without a filter. Note: for lead and PFAS reduction, there may be no detectable sign of exhaustion.
Action: Replace on schedule — do not wait for taste indicators when using for health contaminants.
RO membranes
Signs: TDS of filtered water rises above 50% of original post-installation TDS. Example: if your RO initially produced 15 ppm from 187 ppm source (91.9% rejection), replacement is warranted when filtered TDS rises to 30-40 ppm or above.
Action: Test monthly with a TDS meter. Track the reading in a note on your phone with the date.
Sediment filters (whole-house, RO pre-filter)
Signs: Increased pressure drop across the housing — reduced flow at taps or from RO. Sediment filter housings become heavy with trapped particles.
Action: Replace every 3-6 months regardless, sooner if flow reduction is noticeable.
UV lamps
Signs: No visible sign — UV output degrades invisibly. A lamp that still glows may be producing less than 40 mJ/cm² UV dose.
Action: Replace annually by calendar date. Some systems (Viqua D4 Premium) include electronic lamp age monitoring.
Replace on Schedule, Not on Taste
Carbon filter exhaustion for health contaminants (lead, PFAS) is silent — there is no taste change when these contaminants start passing through an overloaded filter. If you are using a filter for health protection, the only reliable safety signal is the replacement schedule. Set a phone reminder on installation date. Replace when the calendar or gallon limit is reached.