Well Water Filter Change: A Schedule for Every Part
- Guide type
- Buying guide
- Last reviewed
- 2026-11-05
- Sources
- 19 cited
- Lab-tested by us
- No. How we research
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Each part has its own clock. Sediment cartridges: every 3 to 6 months or sooner if pressure drops, per Pentair. Carbon: on the maker's schedule or earlier. UV lamps: yearly for most, every 2 years for VIQUA's PRO series, even if they still glow. RO: carbon blocks every 6 to 12 months, RO cartridges every 12 to 24, per Penn State. Neutralizer media is topped up as it dissolves, and softener resin lasts years. After any change, test the treated water.
The schedule
| Part | When | Signs it’s time |
|---|---|---|
| Sediment cartridge | Every 3 to 6 months or less (Pentair)1; about 12 months or 50,000 gal for a 20-inch cartridge (Pentair FloPlus)2 | Noticeable pressure drop at the tap; change in taste, colour or flow1 |
| Spin-down screen | Flush when sediment shows in the bowl; screen 12 to 24 months (iSpring)3 | Sediment visible through the clear cover |
| Carbon cartridge (whole house) | Maker’s schedule; e.g. 50,000 gal or 12 months (iSpring WGB21B)4 | Taste or odour returns; pressure drop is not reliable5 |
| Iron and manganese cartridge | 50,000 gal at 3 ppm iron, or about 12 months (iSpring FM25B)6 | Stains come back |
| RO carbon blocks | About 6 to 12 months (Penn State)7 | Taste; TDS reading rising |
| RO membrane | About 12 to 24 months (Penn State)7; 2 to 3 years on well water (APEC)8 | TDS reading rising; test the water |
| UV lamp | Yearly for most (about 9,000 h)9,10; every 2 years for VIQUA PRO11 | Lamp-life alarm; a lamp can glow after losing strength12 |
| UV quartz sleeve | Clean at least every 12 months, every 3 to 6 months with mineral-rich water (VIQUA)13; replace every 5 years (LUMINOR)9 | Low-UV alarm |
| Calcite neutralizer media | Refill as it dissolves: weeks to months (Penn State)14 | Media below the maker’s mark; SpringWell says about 10 inches15 |
| Softener resin | Over ten years when protected (Purolite, resin maker)16 | Hard water despite regeneration |
| Greensand media | Regenerated with permanganate or chlorine; no media life published17 | Iron or manganese at the tap |
Our take: when the maker’s schedule and the signs disagree, follow whichever comes first. Nebraska Extension cites tests where carbon performance dropped significantly after 75% of the maker’s rated life5.
What shortens part life on a well
- Sediment and iron load cartridges faster. iSpring rates its iron cartridge at 50,000 gallons only at 3 ppm of iron6.
- Chlorine damages softener resin: Purolite says each 1 mg/L of chlorine reaching the resin cuts its life by half, and chlorine or iron fouling can bring it under a year16. Put dechlorinating carbon ahead of the softener if you chlorinate.
- Unmaintained units can make water worse. Minnesota warns they can make you sick, and that saturated carbon can release what it caught18.
Buying the right replacement
- Match three numbers: size (for example 20 x 4.5 inch “Big Blue”), micron rating, and rated flow. A cartridge rated for less flow than your house uses lets water rush through untreated.
- Watch the flow rating on carbon. Pentek’s EPM-20BB carbon block is rated for 4 gpm19, far below most whole-house flow; iSpring’s iron cartridge is rated 4 to 8 gpm inside a system sold for 156.
- UV parts: genuine only. VIQUA says to use only genuine VIQUA lamps and sleeves11.
Pentek DGD-5005-20
No NSF/ANSI listing found- Micron
- 5 (dual gradient)
- Size
- 4.5 x 20 in
- Flow
- 20 gpm; under 1 psi drop when new
- Fits
- 20 in Big Blue housings
- 5-micron rating for the stage a UV system needs
- High flow for its size
- No gallon rating: change on schedule or pressure drop
- Disposable
Good fit: a Big Blue housing in front of UV or a softener.
Skip it if: heavy sand: use a spin-down ahead or a coarser cartridge.
iSpring F3WGB32BM (FP25B + FC25B + FM25B)
No NSF/ANSI listing found- Stages
- 5-micron sediment, carbon block, iron and manganese
- Iron cartridge
- 50,000 gal at 3 ppm iron; 4–8 gpm
- Carbon and sediment
- 100,000 gal each
- Fits
- iSpring WGB32BM and 20 x 4.5 in housings
- The full set for the WGB32BM in one order
- Standard Big Blue size
- The iron cartridge's 4–8 gpm limits the whole system's flow
- Wears faster above 3 ppm of iron
Good fit: owners of the iSpring WGB32BM, about once a year.
Skip it if: iron above 3 ppm: a tank filter suits better.
After every change
Minnesota’s rule: after installing or servicing treatment, test the treated water to make sure it works18. If a change meant opening the well or the plumbing after a UV unit, chlorinate as the maker asks; see our UV guide.
Questions
How often should I change my whole-house well filter?
For sediment cartridges, Pentair says every 3 to 6 months or less, sooner if pressure at the tap drops noticeably or the taste, colour or flow changes. Well water with sand or iron wears them out faster.
Does a UV lamp need changing if it still lights up?
Yes. Ohio's health department warns a lamp can still glow after losing much of its strength. Most lamps are replaced yearly (about 9,000 hours); VIQUA's PRO lamps every 2 years.
How long does softener resin last?
Resin maker Purolite says it can work reliably for over ten years, but chlorine and iron fouling can cut that to under a year. Each 1 mg/L of chlorine reaching the resin halves its life, which matters if a well chlorinator feeds the softener.
Can I use any brand of replacement cartridge?
For standard sizes, yes, if the size, micron rating and flow match: 20 x 4.5 inch Big Blue cartridges fit Big Blue housings from many brands. For UV, VIQUA says to use only genuine VIQUA lamps and sleeves.
Bottom line
Write down every part, its size and its install date, and set reminders: sediment every 3 to 6 months, carbon and RO prefilters on the maker's schedule, UV lamps yearly (or every 2 years for VIQUA PRO), RO membranes every 1 to 3 years. Check a neutralizer's media level a few times a year. And after each change, or once a year at least, test the treated water.
Related guidesWhat we checked, and what we didn't
- Replacement intervals in Pentair, iSpring, VIQUA, LUMINOR, UV Pure, APEC and SpringWell documents
- Extension guidance from Penn State, Nebraska and Minnesota
- Replacement part numbers and sizes on the makers' pages
- How long parts last on your water: iron, sediment and use change everything
- Greensand media life: no maker or agency publishes one
- A pressure-drop number that means 'change it now': no maker publishes one
Sources
- LR-BB50 Heavy Duty Water Filtration System: Installation and Operation Manual · Pentair (manufacturer)
- FloPlus Heavy Duty Filtration System · Pentair (manufacturer)
- iSpring WSP Spin-Down Sediment Filter · iSpring (manufacturer)
- iSpring WGB21B 2-Stage Whole House Filter · iSpring (manufacturer)
- Drinking Water Treatment: Activated Carbon Filtration (G1489) · Nebraska Extension
- F3WGB32BM Replacement Filter Pack · iSpring (manufacturer)
- Home Water Treatment for PFAS · Penn State Extension
- FAQ: filter replacement schedule · APEC Water Systems (manufacturer)
- BLACKCOMB Owner's Manual · LUMINOR Environmental
- Hallett 500PN Technical Data Sheet · UV Pure Technologies
- H, K, H+, K+, PRO10-PRO50 Owner's Manual · VIQUA
- Ultraviolet Light for Continuous Disinfection · Ohio Department of Health
- FAQs · VIQUA
- Corrosive Water Problems · Penn State Extension
- SCN1-6 Calcite System Instructions · SpringWell (manufacturer)
- Factors that affect softening resin performance and life · Purolite (resin maker), hosted by InspectAPedia
- Iron and Manganese in Private Water Systems · Penn State Extension
- Home Water Treatment (fact sheet) · Minnesota Department of Health
- EPM-20BB Carbon Block Cartridge · Pentair (manufacturer)
Revision history
| 2026-11-05 | First version, built from manufacturer manuals and Penn State, Nebraska, Minnesota and Ohio guidance. |