# Reverse Osmosis Membrane Replacement Cross-Reference: Which 1812 Membranes Fit an Under-Sink System at 50, 75 and 100 GPD > A 1812 RO membrane is 11.74 x 1.75 in per DuPont's data sheet: FilmTec TW30-1812, iSpring MC7 and MC1, APEC MEM-ES-50 and Express Water ROM all fit. | | | |---|---| | Source | https://ownerspec.com/water/parts/reverse-osmosis-membrane-cross-reference-1812/ | | Publisher | OwnerSpec (https://ownerspec.com/) | | Published | 2026-09-13 | | Updated | 2026-09-13 | | Facts verified | 2026-09-13 | | Disclosure | Contains affiliate links. OwnerSpec may earn a commission at no cost to the reader. | --- ## Short answer A 1812 residential reverse osmosis membrane is 11.74 in long and 1.75 in in diameter, the figure DuPont prints for its whole FilmTec TW30-1812 family, and it fits a nominal 2 in inside-diameter pressure vessel. The DuPont TW30-1812-50, -75 and -100, iSpring's Greatwell MC5, MC7 and MC1, APEC's MEM-ES-50 and Express Water's ROM cartridge are all 1812 parts and interchange in that housing. The number that separates them is stabilized rejection: DuPont's 50 and 75 gpd elements are rated 98 percent at 50 psig, the 100 gpd element in the same size drops to 90 percent, and iSpring lists 97 percent TDS for MC5, MC7 and MC1. A tankless system is not a 1812 system: Waterdrop's G3P800 takes the proprietary G3P800-N2RO on a 24-month interval. Published intervals run as short as 1 year (Express Water); APEC's own page states none, so the spec that must match is the diameter, not the gpd. ## Fact sheet - **Answer:** A 1812 residential RO membrane measures 11.74 x 1.75 in and fits a nominal 2 in inside-diameter pressure vessel, per DuPont's FilmTec TW30-1812 data sheet. DuPont's TW30-1812-50, -75 and -100, iSpring's Greatwell MC5, MC7 and MC1, APEC's MEM-ES-50 and Express Water's ROM cartridge are all 1812 parts; a tankless system such as the Waterdrop G3P800 takes a proprietary cartridge instead. - **Applies to:** TFC 1812, 50 GPD; TFC 1812, 75 GPD; TFC 1812, 100 GPD - **Compatibility basis:** DuPont FilmTec TW30-1812 data sheets, Form No. 609-02188-0110 (-24/-36/-50/-75) and 609-00382-0211 (-100), dimensions and pressure vessel fit - **Assumptions:** DuPont prints 11.74 in for the element length; iSpring and Express Water print 11.75 in for theirs. The page treats the two as the same 1812 size, which is how iSpring's own page lists a DuPont element under its MC1US part number.; APEC describes the MEM-ES-50 housing as industry standard 10 inch and publishes no inch dimensions, rejection percent or test pressure; its 1812 fit rests on that description alone.; NSF/ANSI 58 is cited from each maker's own data sheet or product page. NSF's listing database was not reachable when this page was verified. - **Method:** Dimensions, rated flow, test conditions, rejection and intervals copied from each manufacturer's own data sheet or product page; no membrane was tested or measured by OwnerSpec. - **Primary source:** [DuPont/Dow FilmTec TW30-1812 (-24/-36/-50/-75) Membranes data sheet, Form No. 609-02188-0110 (PDF, Lenntech-hosted copy of the Dow document)](https://www.lenntech.com/Data-sheets/Dow-Filmtec-TW30-1812-75-L.pdf) (manufacturer or vendor document) - **Facts verified:** 2026-09-13 - **Last updated:** 2026-09-13 - **Canonical URL (cite this):** https://ownerspec.com/water/parts/reverse-osmosis-membrane-cross-reference-1812/ If the old membrane slid out of a slim tube with a screw cap, keep reading; if it came out as a numbered plastic cartridge that clicks into a head, you own a tankless unit and no part on this page fits it. ## Which membranes are 1812 parts? Every figure below is the maker's published number, from DuPont's FilmTec data sheets (Form No. 609-02188-0110 and 609-00382-0211), iSpring's RO membrane page, APEC's MEM-ES-50 page and Express Water's filter set pages. OwnerSpec has tested none of them. DuPont's sheet states its figures for 250 ppm softened tap water at 77°F (25°C), 15 percent recovery and the specified applied pressure, with element flow varying plus or minus 20 percent. | Membrane | Part no. | Rated GPD | Test pressure | Stabilized rejection | Dimensions (in) | Certification | |---|---|---|---|---|---|---| | DuPont FilmTec TW30-1812-50 | 339138 | 50 | 50 psig | 98% (96.0% minimum) | 11.74 x 1.75 | NSF/ANSI 58, material requirements only, per DuPont's sheet | | DuPont FilmTec TW30-1812-75 | 339146 | 75 | 50 psig | 98% (96.0% minimum) | 11.74 x 1.75 | NSF/ANSI 58, material requirements only, per DuPont's sheet | | DuPont FilmTec TW30-1812-100 | 170102 | 100 | 50 psig | 90% (90.0% minimum) | 11.74 x 1.75 | Not stated on the sheet | | iSpring Greatwell MC5 | MC5 | 50 | Not published | 97% TDS | 11.75 x 1.75 | NSF/ANSI 58, per iSpring's page | | iSpring Greatwell MC7 | MC7 | 75 | Not published | 97% TDS | 11.75 x 1.75 | NSF/ANSI 58, per iSpring's page | | iSpring Greatwell MC1 | MC1 | 100 | Not published | 97% TDS | 11.75 x 1.75 | NSF/ANSI 58, per iSpring's page | | APEC MEM-ES-50 | MEM-ES-50 | 30-50 | Not published | Not published | "Industry standard 10 inch" per APEC | Not stated | | Express Water ROM, 50 GPD | ROM | 50 per the listing title; not on the product page | Not published | Not published | 11.75 x 1.75 | Not stated | | Express Water membrane, 100 GPD | Not published | 100 | Not published | Not published | Not published on the Elite page | Not stated | Two DuPont rows carry no link on purpose: Amazon's current Dow-branded listings for the 75 and 100 gpd sizes are the BW60-1812-75 and the TW30-1812-100HR, different series sold as replacements, not the original part numbers. iSpring's own page is the clearest maker-published cross-fit found: it lists a DuPont-branded FilmTec TW30-1812-100 under its own part number MC1US, as a cross-fit alternative to its house-brand MC1, which keeps a separate part number. Do not trade rejection for throughput without a TDS reading first. DuPont's 100 gpd element gives up 8 points of stabilized rejection against the 50 and 75 gpd elements in the same 1812 size. ## How do you read the housing for size? DuPont's data sheet says the TW30-1812 fits a nominal 2 in inside-diameter pressure vessel: the slim tube on the bracket with a screw cap at one end, not one of the fat 10 in pre-filter housings. Pull the old element and measure across the wrap: 1.75 in is a 1812. iSpring's MC2 is the near miss, 11.75 in long but 2 in across per iSpring's page. Two more numbers from DuPont's sheets bear on fit. Maximum operating pressure is 150 psig for the 50 and 75 gpd elements and 300 psig for the 100 gpd element, and DuPont recommends a 24-hour rinse before first use for a system to meet NSF/ANSI 58. Stage-by-stage part lists for three common hosts are on the [iSpring RCC7](/water/parts/ispring-rcc7-replacement-filters/), [APEC ROES-50](/water/parts/apec-roes-50-replacement-filters/) and [Waterdrop G3P800](/water/parts/waterdrop-g3-g3p800-replacement-filters/) pages. A [10 in standard cartridge](/water/parts/10-inch-standard-water-filter-cartridge-compatibility/) housing holds a pre-filter, not the membrane. ## Which systems do not take a 1812 membrane? | Element or system | Why it is not a 1812 | Source | |---|---|---| | iSpring MC2 (200 gpd) | 11.75 x 2 in: same length, 0.25 in wider | iSpring's RO membrane page | | iSpring MC4 (400 gpd) | 2.8 x 12 in, sold for the RE4T | iSpring's RO membrane page | | iSpring MRO500, MRO600 | Sold only for named tankless systems; no 1812 dimension printed | iSpring's RO membrane page | | iSpring MC600 | Prints 11.75 x 1.75 in but sold only for the RCT600 tankless housing; a matching dimension does not prove interchange with a 1812 pressure-vessel system | iSpring's RO membrane page | | Waterdrop G3P800 (800 gpd tankless) | Proprietary G3P800-N2RO cartridge, 24 months or 2,200 gallons, never described as 1812 | Waterdrop's G3P800 page | Waterdrop publishes no dimensions or rejection percent for the G3P800-N2RO, only the interval. The [tankless RO review](/water/reviews/best-tankless-reverse-osmosis-system/) and the [under-sink RO review](/water/reviews/best-under-sink-reverse-osmosis-system/) compare the two formats on published specs. ## How often does a 1812 membrane need replacing? The makers disagree and DuPont publishes no interval at all. APEC's own MEM-ES-50 page states no replacement schedule; a customer review on that page mentions two years, but that is not APEC's stated guidance. Express Water's filter set page rates the ROM cartridge as a 1-year part, filtering to 1/10,000 micron at 45 to 80 psi and 40 to 100°F, and its Elite page repeats once a year for the 100 gpd tier at 40 to 80 psi. The calendar is the outer bound, not the trigger: a permeate TDS reading that climbs while the pre-filters are fresh means the membrane is due. The [remineralization guide](/water/guides/reverse-osmosis-remineralization-do-you-need-it/) covers the post-membrane stage, and the [GPD and tank size calculator](/water/calculators/reverse-osmosis-gpd-tank-size-calculator/) sizes the membrane rating to the household. **Which 1812 to buy** The DuPont TW30-1812-50 is the only fully specified 1812 sold on Amazon under its original part number (98 percent rejection at 250 ppm, 77°F, 15 percent recovery, 50 psig), and its NSF/ANSI 58 listing covers material requirements only, per DuPont's own sheet, not a reduction claim. The iSpring MC7 prints 97 percent TDS with no test pressure, ppm or temperature, so the two are not directly comparable. If you need a documented spec, buy the DuPont; if your system shipped with an MC7, buy the MC7. Buy neither until you have measured the old element at 1.75 in across. ## The picks - **DuPont FilmTec TW30-1812-50**: The fully specified 1812: 98 percent rejection on a stated test (50 gpd at 50 psig, 98 percent stabilized rejection, 96.0 percent minimum, 11.74 x 1.75 in, NSF/ANSI 58 materials only per DuPont's sheet) Amazon: https://www.amazon.com/dp/B00D43H6GQ/?tag=ownerspec-20 - **iSpring Greatwell MC7**: Like-for-like swap for an iSpring RCC7 family system (75 gpd, 97 percent TDS rejection, 11.75 x 1.75 in, NSF/ANSI 58 per iSpring's page; test pressure not published) Amazon: https://www.amazon.com/dp/B007TBB69W/?tag=ownerspec-20 - **iSpring Greatwell MC1**: 100 gpd in the same 1812 housing (100 gpd, 97 percent TDS rejection, 11.75 x 1.75 in, NSF/ANSI 58 per iSpring's page; iSpring separately lists a DuPont-branded element under part number MC1US as a cross-fit) Amazon: https://www.amazon.com/dp/B007TB9NEC/?tag=ownerspec-20 - **APEC MEM-ES-50**: APEC Essence owners wanting the maker's own part (30-50 gpd, industry standard 10 inch housing per APEC's page; rejection, test pressure and replacement interval not published by APEC (a customer review on the page mentions two years)) Amazon: https://www.amazon.com/dp/B01IIWC55Y/?tag=ownerspec-20 - **Express Water RO membrane, 50 GPD**: Express Water owners on the 1-year schedule (11.75 x 1.75 in, 1/10,000 micron, 45-80 psi, 40-100°F, 1-year life per Express Water's filter set page; 50 gpd per the listing title) Amazon: https://www.amazon.com/dp/B01G4GF9EU/?tag=ownerspec-20 ## Frequently asked questions ### What size is a standard 1812 reverse osmosis membrane? DuPont's FilmTec data sheet lists 11.74 in long and 1.75 in in diameter for the whole TW30-1812 line, with a 0.68 in permeate tube, and states the element fits a nominal 2 in inside-diameter pressure vessel. iSpring and Express Water print 11.75 x 1.75 in for their 1812 elements. Measure the old element across the wrap: 1.75 in is a 1812, 2 in is not. ### Does a higher GPD 1812 membrane reject less TDS? In DuPont's line, yes. The FilmTec data sheets rate the TW30-1812-50 and TW30-1812-75 at 98 percent stabilized salt rejection with a 96.0 percent minimum, and the TW30-1812-100 in the same 1812 size at 90 percent stabilized with a 90.0 percent minimum. All three are tested at 50 psig. iSpring prints 97 percent TDS for its 50, 75 and 100 gpd elements without stating a pressure. ### How often does a 1812 membrane need replacing? DuPont publishes no interval at all. APEC's own MEM-ES-50 page states no replacement schedule; a customer review on that page mentions two years, but that is not APEC's guidance. Express Water's filter set page rates its ROM cartridge as a 1-year part, and its Elite page repeats once a year for the 100 gpd tier. A rising permeate TDS reading with fresh pre-filters signals replacement is due. ### Does a tankless reverse osmosis system use a 1812 membrane? No. Waterdrop's G3P800 page lists its membrane as the G3P800-N2RO, a numbered cartridge on a 24-month interval, never described as 1812. iSpring's MC4, MRO500 and MRO600 are sold only for tankless or high-flow systems with no 1812 dimension printed. iSpring's MC600 does print 11.75 x 1.75 in, but only for the RCT600 tankless housing, not a 1812 pressure vessel. ### Under what conditions does DuPont test a FilmTec 1812 membrane's rejection rate? DuPont's FilmTec TW30-1812 data sheet states that permeate flow and salt rejection are based on 250 ppm softened tap water at 77°F (25°C), 15 percent recovery and the specified applied pressure, which is 50 psig for the 50, 75 and 100 gpd elements. It adds that individual element flow may vary plus or minus 20 percent, and recommends a 24-hour rinse before first use to meet NSF/ANSI 58. ## Sources - [DuPont/Dow FilmTec TW30-1812 (-24/-36/-50/-75) Membranes data sheet, Form No. 609-02188-0110 (PDF, Lenntech-hosted copy of the Dow document)](https://www.lenntech.com/Data-sheets/Dow-Filmtec-TW30-1812-75-L.pdf) (manufacturer or vendor document) - [DuPont/Dow FilmTec TW30-1812-100 High Flow element data sheet, Form No. 609-00382-0211 (PDF, Lenntech-hosted copy of the Dow document)](https://www.lenntech.com/Data-sheets/Dow-Filmtec-TW30-1812-100-L.pdf) (manufacturer or vendor document) - [iSpring, RO Membrane product page (Greatwell MC5, MC7, MC1, MC2, MC4, MC600, MRO500, MRO600 specifications)](https://www.ispringfilter.com/ro-membrane) (manufacturer or vendor document) - [APEC Water, RO Membrane 30-50 GPD for Essence RO Systems (MEM-ES-50) product page](https://www.apecwater.com/products/apec-reverse-osmosis-membrane-30-50-gpd-for-essence-ro-systems) (manufacturer or vendor document) - [Express Water, RO System Filter Set product page (ROM cartridge dimensions, micron, life cycle, pressure and temperature)](https://www.expresswater.com/products/ro-system-filter-set) (manufacturer or vendor document) - [Express Water, Elite RO Filter Set product page (100 GPD, 40-80 psi, once-a-year change)](https://www.expresswater.com/products/elite-ro-filter-set) (manufacturer or vendor document) - [Waterdrop, G3P800 Tankless Reverse Osmosis System product page (G3P800-N2RO replacement interval)](https://www.waterdropfilter.com/products/tankless-reverse-osmosis-system-wd-g3p800-w-fc-1) (manufacturer or vendor document) --- Citation: OwnerSpec, "Reverse Osmosis Membrane Replacement Cross-Reference: Which 1812 Membranes Fit an Under-Sink System at 50, 75 and 100 GPD", https://ownerspec.com/water/parts/reverse-osmosis-membrane-cross-reference-1812/, facts verified 13 September 2026. 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