Evans 5-Stage Ultrafiltration System

Evans 5-Stage at a glance

The 3-Stage and 5-Stage use the identical UF-10Q membrane, rated to 0.01 microns on both manufacturer spec sheets — so pathogen protection is exactly the same between them. What the extra cost actually buys is taste: a granular carbon stage plus a final coconut-shell carbon polisher, on top of the carbon block the 3-Stage already has. That's not a marketing distinction from ordinary coal-based carbon — a structural study in the International Journal of Energy and Water Resources found coconut-shell processing tends to produce a finer, more micropore-dominated structure than coal-based alternatives, close to the molecular size of residual chlorine and the compounds that carry taste and odor. That's the mechanism behind Evans's own description of this stage: coconut-fiber carbon that absorbs residual chlorine and gives the water back a pleasant smell and taste.

That polishing stage's job doesn't stop at chlorine flavor. Chlorinated municipal water — CDMX's included — reacts with the organic matter already present in it to form disinfection byproducts, trihalomethanes among them. A study in Water, Air, & Soil Pollution testing biological activated carbon filtration found meaningful reductions in both trihalomethanes and haloacetic acids as water passed through, though the effect declined as the carbon aged. So a taste that's drifting back toward “pool water” over time isn't just cosmetic — it's usually the same aging cartridge losing capacity for both jobs at once.

Two carbon stages instead of the 3-Stage's one raises a fair question: does more carbon surface mean more opportunity for something to grow on it? Research on point-of-use carbon block filters has found bacterial counts in filter effluent can climb sharply once a cartridge is well past its rated life — but in a multi-stage system like this one, carbon sits upstream of the ultrafiltration membrane, not after it, so the membrane's physical barrier is unaffected either way. It's the reason both carbon stages stay on the same 6-month schedule as the 3-Stage's single one, rather than something to worry about between visits.

One counterintuitive fact worth knowing: despite having two more stages, this system actually loses less pressure than the 3-Stage does — 2 PSI here versus 4 PSI there, per Evans's own spec sheets — because the granular carbon stage sits ahead of the fine carbon block and takes some of the load off it. Evans still specifies the same 20 PSI minimum operating pressure for both systems, though, so if you're not sure what your building actually delivers, here's how to check it — a cheap gauge, or we'll check it for free if you're in our service area. The tradeoff for the extra stage is size: this unit runs to about 8 kg boxed, roughly double the 3-Stage's 3.8 kg — worth a glance if your under-sink cabinet is tight.

See the full comparison across all four systems for what “partial” and “final-stage UV” mean in practice.

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