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Replacement Filters

Replacement Filters

Water Filter System Replacements: The Right Cartridge, Every Time

Whatever's running your water treatment RO, whole-house Big Blue, a softener, or a UV system, we carry the replacement filters, cartridges, media, and parts to keep it working. Use the tools below to find your exact water filter system replacement by model, part number, or size, or call our tech support team if you're not sure what you're looking at.

Now offering yearly filter replacement subscriptions!

  • Big Blue 20-inch GAC Filter
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    Big Blue 20-inch GAC Filter

    $62.00
    The Big Blue 20" GAC filter can be used to replace a current filter or upgrade from the standard carbon block filter. The filter measures 4.5-inch in diameter and 20-inch long and fits all standard...
    GC-4520
    $62.00
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Find Your Replacement Water Filter Fast

Search by Model or Part Number

Every listing in our Individual Replacement Filters collection notes the original part number it replaces, so you can search by your existing filter's part number, even if it's an older or discontinued listing. This cross-reference approach means you don't need to know a brand name, just match the number printed on your current cartridge.

Not Sure What You Have? How to Identify Your System & Measure Your Cartridge

If there's no visible part number, pull the cartridge and measure it. Standard replacement water filters come in four common sizes: 10"×2.5", 20"×2.5", 10"×4.5", and 20"×4.5" (Big Blue). Note the housing size, the micron rating if printed on the old cartridge, and whether it's sediment, carbon, or a specialty media, then match those specs to our catalog or call us at 785-661-2241, and we'll help you identify it.

Shop Replacement Filters by Type

Carbon Block & GAC Filters

Carbon filters, whether solid block or granular activated carbon (GAC), remove chlorine, chloramine, and the tastes and odors that come with them. You'll find both formats across our Big Blue and Slimline replacement categories, sized to match your existing housing.

RO Membranes & Inline Post-Filters

Reverse osmosis systems need their membrane and inline post-filters replaced on separate schedules from the pre-filters.

Membranes Inline Filters

UV Replacement Lamps & Quartz Sleeves

If your setup includes UV disinfection, the lamp and quartz sleeve are separate wear parts with their own replacement schedules.

Shop UV Lamp (Bulb) Replacements

Replacement Filter Kits by System

Drinking RO Kits; Big Blue Whole-House Kits; Specialty Kits

Rather than buying each cartridge separately, most systems are cheaper to maintain with a matched kit. Shop Drinking RO Filter Kits for full drinking water RO change-outs, Big Blue Filter Kits for whole-house sediment/carbon systems, and Specialty Filter Kits for water coolers, aquarium RO/DI setups, and less common configurations. Standard Filter Kits and Portable RO Filter Kits round out the most common household setups.

Understanding Micron Ratings

What a Micron Rating Means & How to Choose?

A micron rating tells you the smallest particle size a filter is built to catch. The lower the number, the finer the filtration, but also the faster it can clog if it's not protected by a coarser pre-filter upstream. Water filter replacement parts are usually staged: a coarser sediment filter goes first to catch sand and grit, protecting a finer filter or carbon block installed after it.

Quick Reference: Which Micron Removes What

Micron Rating What It Removes
20 micron Sand, rust, visible sediment
5 micron Fine silt, suspended particles, cloudiness
1 micron (absolute) Very fine sediment, cysts like Giardia and Cryptosporidium (NSF/ANSI 53)
0.5 micron and below Ultra-fine particles, some bacteria; typically paired with carbon for taste/chemical reduction

How Often Should You Replace Your Water Filter?

Typical Schedule by Filter Type

Filter Type Typical Replacement Interval
Sediment & carbon cartridges 6–12 months
RO membranes 2–5 years
UV lamps ~12 months
Tank media/resin 5–15 years (varies by media)

Signs Your Filter Needs Replacing

A clogged filter typically shows up as noticeably lower water pressure, while a spent carbon filter lets chlorine taste or odor return, even though the water still looks clear. Either sign means it's time for a change, regardless of where you are in the typical schedule.

Well Water vs. City Water Frequency

Well water usually carries more sediment and mineral load than treated municipal water, which means sediment and carbon cartridges on a well system often need replacing closer to the 6-month mark, while city water systems can often stretch toward 12 months. If you're replacing filters noticeably faster than expected, it's worth testing your water to see what's driving the extra load.

Never Run Out

Save with a Filter Replacement Subscription

How Auto-Ship Works, Savings, Never Miss a Change: We offer yearly filter replacement subscriptions so your cartridges ship automatically on the schedule your system actually needs, at a lower cost than ordering one-off, and you never end up running expired filters because you forgot to reorder. Set it once at checkout and adjust or cancel anytime.

Softener, Valve & System Replacement Parts

Fleck / Pentair Rebuild Kits; Brine & Mineral Tanks; Brackets & Housings

Beyond filters, we stock the parts that keep the rest of your system running: Fleck / Pentair Controls & Parts, including rebuild kits for the 5600, 2510, and 9000/9100 series, plus Clack parts and rebuild kits. For tanks, shop Brine Tanks, Mineral & Resin Tanks, and RO Tanks. For housings and mounting hardware, see Brackets and Housings for Filters.

Frequently Asked Questions

How do I know which replacement filter fits my system?

Check the brand and model number printed on your system or housing, or match your original filter's part number. Many of our listings show the older part number they replace. If there's no number visible, pull the cartridge and measure it; standard sizes are 10"×2.5", 20"×2.5", 10"×4.5", and 20"×4.5".

How often should I replace my water filter?

It depends on the filter type and your water quality. Sediment and carbon cartridges typically last 6–12 months, RO membranes run 2–5 years, and UV lamps need replacing about every 12 months. Well water or heavy sediment can shorten those intervals, so watch for dropping pressure or a return of taste and odor as your signal.

What does the micron rating mean, and which do I need?

The micron rating is the smallest particle size a filter is built to trap. A lower number means finer filtration. A 20-micron filter catches sand and rust, a 5-micron filter handles finer sediment, and a 1-micron or below filter targets very fine particles and cysts. Run a coarser pre-filter first to protect your finer filters downstream.

Can I use a compatible replacement filter instead of the OEM one?

Yes. As long as the size, micron rating, and media type match your system, a quality compatible filter does the same job often at a lower cost than the original brand. Look for filters made with NSF/ANSI-tested materials for added peace of mind.

Can I clean and reuse a water filter cartridge?

Most cartridges are single-use and shouldn't be reused, since reusing them reduces filtration performance and risks introducing contamination. Pleated sediment filters are the main exception; some are rinsable and can be reused for a limited number of cycles before replacement.

Is replacing a water filter something I can do myself?

Yes. Most replacements simply twist or snap into place: shut off the inlet and outlet valves, relieve pressure, swap the cartridge, and run water to flush the system. Carbon filters specifically should be flushed for several minutes to clear loose carbon fines before regular use.