Waterspecialist WS638B Water Filter
- Water Filter
- 2
- 2.2 × 4.3 × 7.4 inches
- NSF
A certified two-pack replacement filter for anyone who already owns a system that takes a WS638B-size cartridge.
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How it ranks among the 76 water filters we track
4.6★ across 509 Amazon ratings, Bayesian-smoothed toward the category average.
509 Amazon ratings, weighted on a log scale so huge counts don't drown everything.
Modest tracked demand last month.
Brand identity, imagery, description and spec coverage.
The ProductDome score is separate from the Amazon rating shown above: it combines the Bayesian-smoothed Amazon rating with evidence volume, tracked demand, and data quality across the 76 water filters we track - how the scorecard works · full water filters data report. Confidence: high - strong rating volume and complete data.Last refreshed Aug 4, 2026. Data-computed, not a hands-on test. Compiled by the ProductDome Research Team.
Overview
Waterspecialist packages the WS638B as a replacement water filter cartridge, sold as a two-pack and certified to NSF 42 and NSF 372 for chlorine taste and odor reduction plus lead-free construction.
At roughly 2.2 by 4.3 by 7.4 inches, this is a small in-line or under-sink style cartridge rather than a whole-house or pitcher filter. The dual certification covers standard aesthetic filtration (NSF 42) and lead-free material compliance (NSF 372), the two checks most buyers look for on a replacement cartridge.
- NSF 42 and 372 certified
- Two-pack
- Compact 2.2 x 4.3 x 7.4 in cartridge
- Waterspecialist brand
Who it's for
Fits someone replacing a worn-out compatible cartridge who wants NSF-certified media on hand as a two-pack rather than buying single units repeatedly.
Strengths and trade-offs
Drawn from this product's published specifications.
- NSF 42 and NSF 372 certified
- Sold as a two-pack for less frequent reordering
- Compact cartridge size
- Listing does not specify which systems it fits
- Small size limits it to point-of-use rather than whole-house filtration
Performance notes
Certification to NSF 42 means the media is tested for reducing chlorine taste and odor, while NSF 372 confirms the components meet lead-free material standards, both standard benchmarks for cartridges this size.
Specifications
| Brand | Waterspecialist |
|---|---|
| Model | WS638B |
| Pack Count | 2 |
| Dimensions | 2.2 × 4.3 × 7.4 inches |
| Certification | NSF |
How it compares
This product against the closest alternatives we track in water filters.
| Product | Amazon rating | Ratings | ProductDome score |
|---|---|---|---|
| Waterspecialist WS638B Water FilterThis product | 4.6 / 5 | 509 | 3.8 / 5 |
| Filterlogic FL-RF46 Water FilterFilterlogic | 4.5 / 5 | 6,368 | 4.4 / 5 |
| Golden Icepure GP-RWF0600A Water FilterGolden Icepure | 4.7 / 5 | 3,800 | 4.4 / 5 |
| Glacier Fresh GF-700P Water FilterGlacier Fresh | 4.7 / 5 | 1,500 | 4.3 / 5 |
| Waterdrop WDS-F27 Water FilterWaterdrop | 4.7 / 5 | 39,300 | 4.1 / 5 |
Similar water filters from other brands
Questions about the Waterspecialist WS638B
Common buyer questions answered straight from the product spec data - no fluff, no "it depends".
What does NSF 42 certification mean?
It means the filter has been tested for reducing chlorine taste and odor.
What does NSF 372 add?
It confirms the filter's components meet lead-free material requirements.
How many filters come in the pack?
Two.