APEC ROES-50 Replacement Filters: Which Cartridges Fit the ROES-50 and ROES-PH75, and What Cross-Fits
The APEC ROES-50 takes FILTER-SET-ES (stages 1-3, every 6-12 months) and a MEM-ES-50 membrane every 2-4 years. The ROES-PH75 needs the ESPH sets, not the ES ones.
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Short answer
The APEC ROES-50 takes five cartridges and the ROES-PH75 takes six, all in what APEC’s FILTER-SET-ES page calls the 10 inch industry standard size. APEC’s ROES-50 manual (Ver. 7.3, September 2025) puts the FI-ES-SED10 5 micron sediment filter in stage 1, an FI-ES-CAB10 10 micron carbon block in stages 2 and 3, the MEM-ES-50 membrane in stage 4 (MEM-ES-75 on the ROES-PH75) and the FI-ES-TCR-QC inline carbon filter in stage 5; the ROES-PH75 adds the FI-PHPLUS-QC calcium carbonate filter as stage 6. Stages 1 to 3 are sold as FILTER-SET-ES and change every 6 to 12 months. The complete ROES-50 set is FILTER-MAX-ES50, with the membrane and post carbon on a 2 to 4 year interval on city water and 2 years on a private well. The ROES-PH75 sets are FILTER-SET-ESPH and FILTER-MAX-ESPH. Generic 10 inch cartridges fit the housings, and APEC’s warranty excludes any defect traced to filters it did not sell.
What fits
ROES-50 owners: the 6-12 month change, stages 1-3
APEC FILTER-SET-ES
1 FI-ES-SED10 5 micron sediment + 2 FI-ES-CAB10 10 micron carbon blocks; 10 in size; up to 3,000 gallons
ROES-50 owners at the 2-4 year membrane change
APEC FILTER-MAX-ES50
Stages 1-5: sediment, 2 carbon blocks, MEM-ES-50 TFC membrane, coconut shell post carbon; 3.5 lb set
ROES-50 owners replacing only the membrane
APEC MEM-ES-50
50 GPD TFC spiral wound membrane, 10 in industry standard size; 1 count; 2-4 years city, 2 years well
ROES-PH75 owners: the 6-12 month change, stages 1-3 and 6
APEC FILTER-SET-ESPH
Sediment + 2 carbon blocks + FI-PHPLUS-QC calcium carbonate filter; 4 lb set
ROES-PH75 owners at the 2-4 year membrane change
APEC FILTER-MAX-ESPH
Stages 1-6 including MEM-ES-75 membrane, post carbon and FI-PHPLUS-QC; 5.5 lb set
ROES-PH75 and ROES-UV75 owners replacing only the membrane
APEC MEM-ES-75
75 GPD TFC spiral wound membrane, 10 in industry standard size; 1 count; 2-4 years city, 2 years well
The spec people get wrong is the SKU suffix, not the size: FILTER-SET-ES fits a ROES-PH75’s first three stages and leaves its stage 6 pH filter in place, spent.
Which cartridges fit the ROES-50 and ROES-PH75?
The ROES-50 manual’s component list (page 3) runs sediment pre-filter, carbon block, carbon block, membrane in its housing, inline carbon. APEC’s ROES-PH75 page adds a sixth stage, the pHPlus re-mineralizing calcium filter, and swaps the 50 GPD membrane for a 75 GPD one. Stages 1 to 3 are the 10 inch industry standard size APEC’s FILTER-SET-ES page names.
| Part | Fits stage | Size | Rating (APEC’s published figures) | Sold as |
|---|---|---|---|---|
| FI-ES-SED10 | Stage 1, sediment, both models | 10 in | 5 micron polypropylene (FILTER-SET-ES page) | In FILTER-SET-ES and FILTER-SET-ESPH |
| FI-ES-CAB10, two per system | Stages 2 and 3, carbon block, both models | 10 in | 10 micron extruded carbon block (FILTER-SET-ES page) | In FILTER-SET-ES and FILTER-SET-ESPH |
| MEM-ES-50 | Stage 4, ROES-50 | 10 in membrane housing | 50 GPD at 60 psi, 30 GPD at 50 psi (ROES-50 product page); TFC spiral wound | MEM-ES-50, 1 count or in FILTER-MAX-ES50 |
| MEM-ES-75 | Stage 4, ROES-PH75 and ROES-UV75 | 10 in membrane housing | 75 GPD TFC spiral wound (MEM-ES-75 page) | MEM-ES-75, 1 count or in FILTER-MAX-ESPH |
| FI-ES-TCR-QC | Stage 5, inline post carbon, both models | 10 in inline, quick connect | Coconut shell refining carbon (FILTER-MAX-ES50 page); no micron figure published | In FILTER-MAX-ES50 and FILTER-MAX-ESPH |
| FI-PHPLUS-QC | Stage 6, ROES-PH75 only | 10 in inline | Food-grade calcium carbonate (FILTER-SET-ESPH page) | In FILTER-SET-ESPH and FILTER-MAX-ESPH |
The four single cartridges are not linked: no standalone listing for them was opened for this page.
The set names are not parallel across the two models. APEC’s product pages use FILTER-SET-ES and FILTER-MAX-ES50 for the ROES-50, and FILTER-SET-ESPH and FILTER-MAX-ESPH for the ROES-PH75; there is no plain FILTER-MAX-ES.
What else fits the same housings?
APEC’s own pages settle the fit question. The FILTER-SET-ES page says the set is compatible with most other industry standard size under-counter RO systems, and the MEM-ES-75 page says the membrane will fit in most commonly available housings. The reverse holds: another maker’s 10 inch cartridge or residential TFC membrane drops into these housings.
| Alternative | Same size? | Rating | What differs from the APEC part |
|---|---|---|---|
| Generic 10 in sediment cartridge | Yes, per APEC’s 10 inch industry standard wording | Set by the maker; APEC’s stage 1 is 5 micron | The warranty clause below; micron rating must be read off the alternative’s own sheet |
| Generic 10 in carbon block | Yes | Set by the maker; APEC’s stages 2 and 3 are 10 micron | The warranty clause; no capacity figure to compare against FILTER-SET-ES’s 3,000 gallons unless the maker publishes one |
| Generic 50 or 75 GPD residential TFC membrane | Yes, standard 10 in membrane housing | GPD rating set by the maker | The manual’s NSF/ANSI 58 line covers the system as sold with APEC’s membrane; APEC publishes no test with another membrane fitted |
| Generic inline post carbon with quick connect fittings | Inline, fitting size not published by APEC | Set by the maker | The manual does not state the tube size at stage 5, so this page cannot confirm the fitting |
No generic listing was opened in Chrome for this page, so none is linked; the FILTER-SET-ES pack of three is the only stages 1 to 3 set with a verified listing here.
The warranty is the real difference. Non-covered defect number 3 in the manual’s Limited Product Warranty (page 38) is the use of replacement parts, filters, membranes or other accessories that are not sold or manufactured by APEC for use with this particular product. The manual gives the warranty term as 1 year from the date of purchase, so the clause matters most on a system under a year old.
Whole-house housings are a different size: the iSpring WGB32B and Express Water WH300SCKS pages cover 20 x 4.5 in Big Blue cartridges, which do not fit under a sink.
How often do they need replacing?
The maintenance schedule on page 20 of the ROES-50 manual is the only interval APEC publishes, and it splits by water source.
| Stage | APEC part | City water | Private well |
|---|---|---|---|
| 1 to 3, pre-filters | FILTER-SET-ES | Every 6 to 12 months | Sooner than 6 to 12 months |
| 4, membrane | MEM-ES-50 or MEM-ES-75 | Every 2 to 4 years | Every 2 years |
| 5, post carbon | FI-ES-TCR-QC | Every 2 to 4 years, with the membrane | Every 2 to 4 years, with the membrane |
| 6, pH (ROES-PH75) | FI-PHPLUS-QC | Every 6 to 12 months (FILTER-SET-ESPH page) | Not stated separately |
| Housing O-rings | Not a cartridge | Every year, or at each pre-filter change | Same |
| Housings | Not a cartridge | Every 5 years | Same |
The FILTER-SET-ES page adds a capacity figure, up to 3,000 gallons through the three pre-filters, without saying which stage reaches it first.
Amazon’s title for FILTER-MAX-ESPH says 1 Year Set. Read that as shorthand: apecwater.com’s page for the same set puts stages 1 to 3 and 6 at 6 to 12 months and stages 4 and 5 at 2 to 4 years.
The manual’s standard operating conditions (page 38) frame every interval: 40 to 85 psi, 40 to 100 F, feed TDS up to 2,000 ppm and pH 2 to 11. On a private well, the manual’s shorter intervals assume you know the feed water; the well water test panel guide lists what to have tested before the first cartridge change.
Which set to buy
The APEC sets are the manual’s exact parts, and the price of that is a range, not a number: 6 to 12 months for the pre-filters, 2 to 4 years for the membrane, with no published trigger for which end you are at. A generic 10 inch cartridge fits the same housing for less and costs you the 1 year warranty. For a ROES-50, fit FILTER-SET-ES at the 6 to 12 month change and FILTER-MAX-ES50 when the membrane is due. For a ROES-PH75, the equivalents are FILTER-SET-ESPH and FILTER-MAX-ESPH ; the ES sets leave the pH filter spent. Skip the complete sets if the membrane went in under 2 years ago: the manual’s shortest membrane interval is 2 years, and you would be paying for stages 4 and 5 you do not need yet.
Frequently asked questions
Does the APEC FILTER-SET-ES fit the ROES-PH75?
APEC's FILTER-SET-ES product page lists the ROES-PH75 among compatible systems, so the three cartridges drop into stages 1 to 3 of either model. It leaves the ROES-PH75's stage 6 FI-PHPLUS-QC calcium carbonate filter unchanged. APEC sells the four together as FILTER-SET-ESPH, which its page puts on the same 6 to 12 month interval as stages 1 to 3.
Do generic 10 inch cartridges void the APEC ROES-50 warranty?
APEC's ROES-50 manual (Ver. 7.3, September 2025) lists as a non-covered defect any use of replacement parts, filters, membranes or accessories not sold or manufactured by APEC for that product. The clause does not say a generic cartridge will not fit; APEC's own FILTER-SET-ES page calls the size 10 inch industry standard. It only removes warranty cover for the 1 year term.
How often does the APEC MEM-ES-50 membrane need replacing?
The maintenance schedule on page 20 of APEC's ROES-50 manual gives the stage 4 membrane 2 to 4 years on city water and 2 years on private well water. The stage 5 FI-ES-TCR-QC carbon filter carries the same 2 to 4 year figure, and the manual says it is best replaced together with the membrane, which is what the FILTER-MAX-ES50 set packages.
Is FILTER-MAX-ES the complete set for the ROES-50?
APEC's product pages use FILTER-MAX-ES50 for the ROES-50 complete set (stages 1 to 5: sediment, two carbon blocks, membrane, post carbon) and FILTER-MAX-ESPH for the six-stage ROES-PH75 set, which adds the FI-PHPLUS-QC filter. There is no plain FILTER-MAX-ES listing on either apecwater.com or Amazon, so a search for that name lands on the wrong page.
What else does APEC say to replace besides the cartridges?
The ROES-50 manual's maintenance schedule recommends new filter housing O-rings every year or at each change of the three pre-filters, and new housings every 5 years. The same table sets the operating window the cartridges run in: 40 to 85 psi feed pressure, 40 to 100 F feed temperature, feed TDS up to 2,000 ppm and pH 2 to 11.
Sources
- APEC ROES-50 Installation Instruction and Owner's Manual (Essence RO System), Ver. 7.3, September 2025 (PDF)
- APEC ROES-50 product page (specification summary)
- APEC ROES-PH75 product detail page
- APEC FILTER-SET-ES pre-filter set for Essence RO systems, stages 1-3, product page
- APEC FILTER-SET-ESPH pre-filter set for Essence 75 GPD pH RO systems, stages 1-3 and 6, product page
- APEC FILTER-MAX-ES50 complete filter set for Essence ROES-50, stages 1-5, product page
- APEC FILTER-MAX-ESPH complete filter set for Essence 75 GPD pH six-stage systems, stages 1-6, product page
- APEC MEM-ES-75 reverse osmosis membrane 75 GPD for Essence RO systems product page
- NSF International, NSF/ANSI 58: Reverse Osmosis Systems
- Amazon listing B00I11HUGW, APEC FILTER-SET-ES (listing title and pack size only)
- Amazon listing B00I5WSO8A, APEC FILTER-MAX-ES50 (listing title and pack size only)
- Amazon listing B00O4CJVEQ, APEC FILTER-SET-ESPH (listing title and pack size only)
- Amazon listing B00OABQCES, APEC FILTER-MAX-ESPH (listing title and pack size only)
- Amazon listing B01IIWC55Y, APEC MEM-ES-50 (listing title and pack size only)
- Amazon listing B01IIXH7JW, APEC MEM-ES-75 (listing title and pack size only)
