How often should I replace my water filter?

It depends entirely on the filter type — there's no universal schedule. NSF International's own guidance is to follow the manufacturer's rated gallon capacity or time interval rather than a fixed rule, since it varies by water quality and usage. As a rough guide: pitcher and fridge filters every 2-6 months, sediment pre-filters every 3-6 months, under-sink carbon cartridges every 6 months, RO membranes every 2-3 years, UV bulbs annually, and whole-house tank media every 6-10 years.

What happens if I don't change my water filter on time?

Two things get worse at once: contaminant reduction drops as the media saturates, and an overdue cartridge can become a breeding ground for bacteria, since wet carbon and organic buildup are exactly what microbes need. NSF and WQA both flag this as the main reason to stick to the rated schedule rather than 'it still tastes fine' — taste is the last thing to change, not the first.

How do I know when my reverse osmosis membrane needs replacing?

Test your water's TDS (total dissolved solids) with a cheap TDS meter. A healthy RO membrane should reject roughly 90-98% of dissolved solids, so if your treated water's TDS climbs toward 10% or more of your tap water's TDS, the membrane is failing even if the water still tastes fine. Most membranes last 2-3 years under normal use; heavy sediment or an overdue pre-filter shortens that.

How often should I add salt to my water softener?

Check the brine tank monthly and refill when it drops below about a third full — most households go through a 40lb bag every 4-8 weeks depending on water hardness and household size. Running the tank empty lets hard water bypass the resin bed untreated, which is the most common softener complaint that turns out to just be an empty salt tank.

Do fridge and pitcher filters really need replacing every 2-6 months?

Yes, and the range varies more than people expect by brand. Brita and PUR pitcher filters are rated for roughly 40 gallons (about two months) on their standard cartridges; ZeroWater's 5-stage filters are rated for only 15-20 gallons because the extra ion-exchange stage saturates faster. Fridge filters (GE, Whirlpool/everydrop, Samsung) typically run 150-300 gallons or about six months. Past the rating, flow slows and contaminant reduction — not just taste — drops off.

Water Filter Maintenance Schedule 2026: How Often to Replace Every Type

Quick Answer: Replacement schedules vary by filter type, not by one universal rule: pitcher and fridge filters every 2-6 months, sediment pre-filters every 3-6 months, under-sink carbon cartridges every 6 months, RO membranes every 2-3 years, UV bulbs every 12 months, and whole-house tank media every 6-10 years, according to NSF International’s own filter-replacement guidance. The one rule that applies across every filter type: go by the manufacturer’s rated gallons or months, not by taste — an overdue filter can start growing bacteria before it tastes any different.

Every product review on this site covers which filter to buy — this guide is the piece that comes after: how long each part actually lasts, what it costs to keep running, and the warning signs that mean it’s overdue.

Replacement schedule by filter type

Filter type	Typical interval	Warning sign if overdue	Approx. annual cost
Pitcher / fridge filter	2-6 months	Slow flow, taste/odor returns	$40-$100
Faucet-mount carbon	2-3 months	Reduced flow, taste returns	$60-$120
Under-sink carbon cartridge	6 months	Taste/odor returns, slower fill	$60-$150
Sediment pre-filter	3-6 months	Visibly discolored, pressure drop	$40-$80
RO membrane	2-3 years	Rising TDS in treated water	$40-$80/yr amortized
RO carbon post-filter	6-12 months	Taste returns even with good membrane	$20-$40
UV sterilization bulb	12 months (fixed)	None visible — bulb still glows, output has faded	$40-$80
Whole-house tank media (catalytic carbon)	6-10 years / ~1M gal	Chlorine taste/odor returns	~$40 (prefilter only)
Water softener resin	10-15+ years	Hard-water spots return despite full salt tank	$0 (just salt)
Water softener salt	Check monthly, refill as needed	Hardness returns, salty taste if bridged	$60-$150

Why “it still tastes fine” is the wrong test

NSF International’s own guidance on changing water filters is blunt about this: there’s no single universal replacement schedule, and the right interval is whatever the manufacturer certified the cartridge for — a specific gallon capacity or month count, tested under NSF/ANSI 42, 53, or 58 for that exact filter. That number, not how the water tastes, is what determines when contaminant reduction starts to fall off. Water quality and usage volume both push the real-world number around, which is why every product review on this site lists a gallon and a time estimate rather than picking one.

The bigger risk with an overdue filter isn’t a slightly worse taste — it’s what’s living inside a saturated cartridge. A carbon filter that’s absorbed everything it can hold is also a wet, organic environment bacteria can colonize, which is the specific failure mode NSF and WQA guidance is written to prevent. Taste is usually the last thing to change, not the first.

Point-of-use filters: pitcher, faucet, under-sink

Pitcher/fridge filters vary more by brand than people expect. Brita and PUR pitcher cartridges are rated around 40 gallons (about two months) on their standard filter; ZeroWater’s 5-stage filters saturate faster at 15-20 gallons, since the extra ion-exchange stage that gets it to a 0 TDS reading is also the stage that clogs first. Fridge filters (GE, Whirlpool/everydrop, Samsung) typically run 150-300 gallons, about six months.
Faucet-mount filters like the PUR Plus run roughly 100 gallons or three months per cartridge — shorter than under-sink because the cartridge is smaller.
Under-sink carbon cartridges last longer per swap, typically 600-800 gallons or six months, because there’s more room for a bigger cartridge under the cabinet.

Universal Replacement Filter Cartridges

Compatible carbon/sediment cartridges · most under-sink and RO systems

Most under-sink and RO systems use a standard cartridge size across brands, so generic replacement carbon and sediment cartridges are usually a direct swap — check your system's cartridge dimensions before ordering to be sure.

Check price on Amazon →

Replacement filters on time, every time — Prime ships them free in two days, so a sediment pre-filter or RO cartridge shows up before the old one’s actually spent; you can try Prime free for 30 days.

Reverse osmosis: membrane, pre-filter, and post-filter on different clocks

An RO system has three parts on three different replacement clocks, and mixing them up is the most common RO maintenance mistake:

Sediment pre-filter: every 3-6 months. Its job is to protect the membrane from particulate damage — running it past its rating shortens the membrane’s life, not just its own.
RO membrane: every 2-3 years. The most expensive part and the one people forget, because a failing membrane doesn’t necessarily change the water’s taste. Test with a TDS meter — see our best TDS meter guide — and if your treated water’s TDS climbs toward 10% or more of your tap water’s reading, the membrane needs replacing even if it still tastes clean.
Carbon post-filter: every 6-12 months. This is the “polish” stage right before the faucet, and it’s often the one that actually controls taste — a spent post-filter can make even a healthy membrane’s output taste flat.

For the systems these numbers apply to, see our best reverse osmosis system guide.

UV, whole-house tanks, and water softeners

UV sterilization bulbs run on a fixed 12-month calendar, not a usage meter. A UV bulb keeps glowing well past a year, but its germicidal output fades with use — the drop isn’t visible, so the only reliable schedule is the calendar, not “it still lights up.” See our best UV water filter guide.
Whole-house catalytic-carbon tanks — like the SpringWell CF1 covered in our best whole-house water filter guide — are the lowest-maintenance category on this list. The tank media itself lasts roughly one million gallons, about 6-10 years, and the only regular part is a $20-$40 sediment pre-filter every 6-9 months. Full cost breakdown is in our whole-house water filter cost guide.
Water softener resin is the most durable component in any home water system — a properly maintained ion-exchange resin bed can run 10-15+ years, and some manufacturers rate it even longer with clean, iron-free water. What actually needs regular attention is the salt: check the brine tank monthly and refill below about a third full, since running it empty lets hard water bypass the resin untreated. See our best water softener guide.

The bottom line

There’s no single “change your filter every X months” rule — NSF’s own guidance is to follow each filter’s rated gallons or months, because the right number depends on the filter type, your water quality, and how much you use. Point-of-use filters (pitcher, faucet, under-sink) run on the shortest clocks, 2-6 months; RO systems split into three parts on three different schedules (3-6 months for the pre-filter, 2-3 years for the membrane, 6-12 months for the post-filter); UV bulbs go by a fixed annual calendar regardless of usage; and whole-house tanks and softener resin are the low-maintenance end at 6-15+ years. The one habit worth building regardless of filter type: replace on the rated schedule, not when the taste changes — by the time you can taste the difference, contaminant reduction has already dropped.

Replacement intervals are manufacturer-rated averages — check your specific system’s documentation, and tap the button above to check current Amazon prices.