PUREPLUS 1 Micron 2.5" x 10" Whole House CTO Carbon Water Filter Cartridge Replacement for Under Sink Water Filter System, Dupont WFPFC8002, WFPFC9001, FXWTC, SCWH-5, WHEF-WHWC, WHCF-WHWC, AMZN-SCWH-5, 4Pack

Why I tried the PUREPLUS CTO10

I wanted a simple, reliable way to knock down chlorine taste and catch fine grit in a standard 10 x 2.5-inch housing—without stepping up to a bulky “big blue” system. The PUREPLUS CTO10, a 1‑micron coconut shell carbon block, checked the right boxes: widely compatible, NSF/ANSI 42 certified by IAPMO for chlorine reduction, and sold in a budget-friendly four-pack. I installed it first as a point‑of‑entry (whole‑house) filter on municipal water, then moved a second cartridge into an under‑sink housing for a dedicated drinking line to see how it behaved in both roles.

What it is and where it fits

At its core, this is a tight (1‑micron) CTO carbon block designed for standard 10 x 2.5-inch housings—the same footprint used by many common systems from DuPont, GE, Whirlpool, Pentek, Culligan, and others. It’s not brand-locked, which makes it a useful replacement for a long list of models. The coconut‑shell carbon block is dense and well‑molded, with clean end caps and consistent sealing surfaces. You don’t get fancy packaging or accessories; just what you need: four individually wrapped cartridges that drop in and seal properly.

The headline spec is NSF/ANSI 42 certification for chlorine taste and odor reduction. That’s the right certification for aesthetic improvements, and it matters if you care about validated claims rather than just marketing copy. PUREPLUS also touts additional international certifications and ISO9001 manufacturing, which won’t change your water on their own but speak to process consistency.

Installation and first flush

Installation was straightforward. I shut off the supply, depressurized the housing, swapped the old cartridge for the CTO10, and lubed the O‑ring with a food‑grade silicone grease before reattaching the sump. As with any new carbon block, the first flush is key: I ran water for a few minutes until the initial carbon fines cleared. After that, the water ran crystal clear with no visible particulates.

One small note: this is a tight 1‑micron block. If your water has visible sediment, put a coarser prefilter (5–20 micron) upstream to extend the CTO10’s life. When I tested it as the only filter on the whole‑house line, it worked, but I saw its benefits and lifespan improve noticeably when paired with a pleated prefilter.

Performance: taste, odor, and clarity

• Chlorine and taste: On city water, the taste improvement was immediate. The chlorine edge disappeared from cold taps within minutes of flushing, and coffee/tea no longer carried that pool‑side note. This matches what I expect from a good carbon block verified for 42 performance.

• Sediment capture: The 1‑micron rating does what it says. Fine silt that made glasses look hazy on bad days was gone, and clear ice cubes stayed clear. After a few weeks in whole‑house use, the cartridge’s surface showed a uniform grayish tint typical of captured fines—encouraging, if a reminder it’s working.

• Odor control: Musty odors that occasionally cropped up after hydrant flushing were removed. If your supply has seasonal taste swings, it’s the kind of filter that smooths them out.

Flow and pressure drop

Any 1‑micron 10-inch carbon block adds some resistance. In my whole‑house test, a single shower plus a running faucet produced a mild but noticeable softening of flow compared to a 5‑micron sediment cartridge. It wasn’t disruptive, but if you have a large household with simultaneous high‑flow demands, you’ll feel it.

Under the sink, flow was a non‑issue. On a dedicated cold drinking line, the CTO10 delivered fast pours and excellent taste. That’s the scenario where a 1‑micron carbon block really shines: polishing the last bit of chlorine and catch‑all particles without burdening the entire home’s flow.

If you need whole‑house filtration and want to stay with 10 x 2.5-inch cartridges, consider running this behind a 5‑micron sediment stage, or use two housings in parallel to reduce pressure drop. For larger homes, a 4.5-inch “big blue” carbon block may be the better match for flow.

Capacity and lifespan

PUREPLUS rates this filter up to about 13,000 gallons with a suggested 3–6 month change interval. In practice, lifespan depends on two things:

• Chlorine load (municipal systems vary)
• Particulate load (the finer the block, the faster it will clog on dirty water)

On treated city water with a modest chlorine residual and not much sediment, I was comfortable targeting the upper end of that 3–6 month window. On a line that sees periodic turbidity or on a private well, I’d plan for the shorter end unless you add a prefilter.

Signs it’s time to change:
- Taste or odors begin to return
- Flow/pressure noticeably drop
- Cartridge surface looks heavily darkened or fouled

I recommend installing inexpensive pressure gauges before and after the filter housing. A 10–15 psi increase in differential since installation is a good trigger for replacement.

Build quality and consistency

The cartridges I tested were well finished with even carbon density and solid end caps. Seals were consistent, and I saw no channeling or bypassing. The initial fines rinse‑out was minimal and cleared quickly. PUREPLUS highlights 400 psi pressure testing and water‑hammer testing at the manufacturing level; I obviously didn’t replicate those lab conditions, but the housings and cartridges handled normal household spikes without drama.

What it won’t do

It’s important to understand the limits of a CTO block:

• It’s not a lead or PFAS filter. If you need reduction of metals or specific organics, look for NSF/ANSI 53 (or 401 for certain emerging contaminants) with explicit claims.
• It isn’t a disinfectant. If you have microbial concerns, use appropriate treatment (UV, chlorination) upstream.
• It won’t soften hard water. Pair with a softener if scale is an issue.
• On heavy iron wells, a carbon block is not a substitute for iron removal. It may reduce metallic taste, but dissolved iron needs targeted treatment.

Set expectations correctly, and you’ll be pleased with what this filter is designed to do—make water taste better and look cleaner.

Best use cases

• Under‑sink polishing filter for drinking and cooking water
• Whole‑house chlorine taste/odor control on cleaner municipal supplies
• Second stage after a 5–20 micron sediment prefilter to catch fines and improve clarity

Tips for getting the most out of it

• Flush thoroughly on first install and after any cartridge swap.
• Use a sediment prefilter upstream on turbid supplies to extend life.
• Sanitize the housing annually with a dilute bleach solution, then rinse and re‑flush.
• Lubricate O‑rings lightly and keep a spare set on hand.
• After vacations, run the tap for a minute before drinking—stagnant water can pick up stale tastes in any carbon filter.

Value and buying in a four‑pack

The four‑pack makes sense. CTO blocks are consumables, and having spares avoids emergency runs when flow starts to drop. Price per cartridge is competitive with name‑brand replacements, and compatibility with common models means you’re not locked into a proprietary ecosystem.

Pros and cons

Pros
- Noticeable taste and odor improvement backed by NSF/ANSI 42 certification
- Tight 1‑micron filtration captures fine silt and improves clarity
- Broad compatibility with standard 10 x 2.5-inch housings
- Good build quality and consistent sealing
- Strong value in a four‑pack

Cons
- Higher pressure drop than 5‑micron or pleated alternatives
- Lifespan can shrink on sediment‑heavy supplies without a prefilter
- Not designed for metals, PFAS, or microbial reduction

Recommendation

I recommend the PUREPLUS CTO10 for anyone who needs a dependable 1‑micron carbon block in a standard 10 x 2.5-inch housing, especially as an under‑sink polishing filter or as part of a two‑stage whole‑house setup. It does exactly what a CTO block should—removes chlorine taste and odor and snags fine particulates—without asking you to buy into a proprietary system. If you’re running multiple showers at once or battling heavy sediment, plan around its tighter micron rating with a prefilter or a larger‑format carbon block. Used in the right role, it’s a cost‑effective, certified way to make everyday water taste cleaner and look clearer.