Fine cloudiness that a sediment filter lets through. A reverse osmosis membrane you want to protect. A household that wants a physical barrier against microbes, not just better taste. Carbon improves taste and chemistry, but it does not strain out bacteria. A membrane does.
This replacement ultrafiltration (UF) water filter membrane holds back bacteria, protozoan cysts, colloids and other fine particles while water and dissolved minerals pass through. The standard drop-in cartridges use a pleated UF membrane with a 0.1 micron nominal rating. There is no drain line and no wastewater. Choose standard 2-7/8" x 9-3/4" and 2-7/8" x 20" drop-in cartridges, an inline/sealed cartridge with JACO or Quick Connect fittings, or a compact capsule.
At a glance
- 0.1 micron pleated UF membrane in the standard sizes: far finer than a typical sediment or carbon stage
- Reduces bacteria and cysts such as Giardia, along with colloids and fine particles
- Keeps the minerals: dissolved minerals pass through, so water keeps its natural taste
- No drain, no wastewater, no electricity
- Long service life: typically 24 to 36 months, in five formats
What you are looking at
The standard drop-in sizes hold a pleated ultrafiltration membrane wrapped around a polypropylene core, inside a slotted outer cage. Both ends are open (double open end) and seal against the housing with silicone gaskets. Everything else in the cartridge, from the membrane and its support layers to the cage, core and end caps, is polypropylene, a chemically inert plastic, and the materials comply with US FDA regulations for food and beverage contact. Pleating gives the membrane a large filtering area, which keeps flow high and service life long. The inline/sealed version is a self-contained cartridge with JACO or Quick Connect fittings, and the capsule is the compact format used after the storage tank on some under-sink systems.
How ultrafiltration works
A folded barrier
Pleating folds a large membrane surface into a small cartridge. Your line pressure pushes water through the membrane from the outside in. The pores are fine enough that most bacteria, protozoan cysts such as Giardia and Cryptosporidium, colloids and fine particles are held back on the membrane surface while clean water passes into the core and on to your tap.
Why it keeps the minerals
Ultrafiltration separates by size. Dissolved minerals such as calcium and magnesium are far smaller than the pores, so they pass straight through. That is the difference from reverse osmosis: UF does not demineralize, does not soften and does not send water to drain. It removes particles and microbes, not dissolved chemistry.
Viruses
Viruses are the smallest microbes, and many are smaller than the membrane's 0.1 micron pores. Ultrafiltration reduces them only partially, so where viruses are a specific concern pair it with UV or reverse osmosis rather than relying on it alone.
Why flow slowly drops
Everything the membrane holds back stays on its surface. Over months that layer builds, and flow gradually falls. A noticeable drop in flow is the membrane telling you it is time for a new one.
What it reduces
Primary targets:
- Bacteria
- Protozoa and cysts, such as Giardia and Cryptosporidium
- Colloids, turbidity and other fine particles
Also reduced: viruses, partially; pair with UV or reverse osmosis where viruses are a specific concern.
Not designed to treat: dissolved chemicals such as chlorine, chloramine, VOCs, lead, fluoride, nitrate and arsenic; hardness; or total dissolved solids. For those, pair it with the SMART Filter Cartridge, a carbon block or reverse osmosis. On water known to be contaminated with bacteria, add UV disinfection and test regularly.
Why Crystal Quest
- The inlet stage of our own RO systems. Every Thunder under-sink reverse osmosis system starts with this UF cartridge, so a replacement matches what the system was built around.
- Five formats. Standard 10-inch and 20-inch drop-in sizes with a 0.1 micron membrane, inline/sealed with JACO or Quick Connect fittings, and a capsule.
- Over 1,000,000 people served since 1994. Crystal Quest builds under ISO 9001 quality management and has made water filtration in the USA for over 30 years.
- Lifetime support. Call, email or chat with our water filtration team whenever you have a question.
Where it fits
- Thunder under-sink RO: first pre-filter at the inlet, the 2-7/8" x 9-3/4" UF (CQE-RC-04055), ahead of SMART Plus and the carbon block
- Thunder 2000 and 4000: add a UF capsule after the storage tank; check the part number on your existing capsule
- Voyager replaceable systems: first stage in the double (UF, then SMART) and the triple (UF, SMART, then carbon block)
- Whole house cartridge systems that list the 2-7/8" x 20" size (CQE-RC-04056)
- Inline/sealed format: choose JACO (CQE-RC-04039) or Quick Connect (CQE-RC-04039Q) to match the connections on your current cartridge
Common questions
Is this a reverse osmosis membrane?
No. Ultrafiltration holds back particles, bacteria and other material larger than its pores, while water and dissolved minerals pass through. Reverse osmosis is a separate, much finer membrane stage that also removes dissolved solids.
What is the difference between ultrafiltration and reverse osmosis?
UF separates by particle size and keeps minerals, with no wastewater. RO pushes water through a far tighter membrane that removes most dissolved solids and sends a share of water to drain. Many Crystal Quest RO systems use both: UF first, RO after.
Does UF remove viruses?
Only partially. Many viruses are smaller than the membrane's pores. Where viruses are a specific concern, pair UF with UV or reverse osmosis.
Which format do I need?
Match the cartridge you are replacing: a standard 2-7/8" x 9-3/4" or 2-7/8" x 20" drop-in cartridge, an inline/sealed cartridge with JACO or Quick Connect fittings, or a capsule. Check the part number on the old cartridge.
How long does a UF cartridge last?
Typically 24 to 36 months. Replace it sooner if the flow drops. Actual life depends on feed water quality, system configuration and usage.
Does it soften water or remove dissolved minerals?
No. Dissolved minerals pass through an ultrafiltration membrane, so it does not soften water or lower dissolved solids the way reverse osmosis does.
UF membrane specifications
The membrane rating applies to the standard drop-in sizes. Replace sooner if the flow drops.
| SKU | SIZE | TYPICAL REPLACEMENT |
| CQE-RC-04055 | 2-7/8" x 9-3/4" | 24 to 36 months* |
| CQE-RC-04056 | 2-7/8" x 20" | 24 to 36 months* |
| CQE-RC-04039 | Inline/Sealed | 24 to 36 months* |
| CQE-RC-04059 | Capsule | 24 to 36 months* |
The inline/sealed cartridge is also offered with Quick Connect fittings (CQE-RC-04039Q).
Membrane and filtration
| Membrane | Pleated ultrafiltration (UF), double open end |
| Membrane rating | 0.1 micron nominal, 85 percent efficiency (2-7/8" x 9-3/4" and 2-7/8" x 20" drop-in sizes) |
| Reduces | Bacteria, protozoan cysts, colloids, fine particles; reduces viruses partially |
| Passes through | Water and dissolved minerals |
| Wastewater | None; no drain connection |
| Construction (drop-in sizes) | Cartridge ratings (drop-in sizes) |
| • Ultrafiltration membrane | • Maximum temperature: 176° F (80° C) |
| • Polypropylene membrane and support layers | • Maximum pressure drop across the cartridge: 60 psi (4 bar) at 68° F (20° C) |
| • Polypropylene slotted cage, core and end caps | • Maximum pressure drop at 176° F (80° C): 35 psi (2.4 bar) |
| • Silicone gaskets • Double open end |
• Protect from freezing. In a complete system, follow the system's own pressure and temperature range. |
*Typical replacement range. Actual life depends on feed water quality, system configuration and usage.