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Our Verdict (Best for)
The Culligan US EZ-4 under sink water filter is fairly easy to set up, use, and maintain, with a fast flow from the dedicated faucet. But we ran into a hiccup when the ½” water feed valve didn’t fit our ⅜” supply, and no adapter was included. On the plus side, the filtered water tasted and smelled perfect, and the Culligan achieved decent results in our lab testing for contaminant reduction. It also holds 66 NSF certifications for contaminant reduction, although most are for easy-to-remove organics. Still, even considering the very affordable upfront costs and below-average maintenance fees, we aren’t thrilled with the cheap plastic parts, including the plastic faucet that appears like chrome but feels flimsy. Bottom line: There are better budget picks out there with sturdier parts.
The Culligan US-EZ-4 is an under sink water filter that requires a plumbing connection and comes with an extra faucet. It’s designed for use as a drinking water filter and can purify both tap water and properly disinfected well water.
As usual, we’ve tested the system with our own hands:
- Hands-on experience: We installed/assembled, used, and maintained it.
- Filtration effectiveness: We sent an unfiltered and a filtered tap water sample to a professional lab for analysis in order to determine real-life contaminant reduction capabilities. Plus, we checked for NSF certifications and other test data.
- More testing: We performed a taste & odor test and a filtration speed test.
- All other product aspects: We considered initial + long-term cost, product warranties, additional features, frequent customer complaints, etc.
Contents
Overall Rating: /5.00
Filtration: /5.00
Usability: /5.00
Costs: /5.00
| Type: | Under Sink Water Filter |
| Price (May 5, 2025, w/o Short-Term Sales): | $86.15 |
| Estimated Yearly Cost (May 5, 2025): | ~$100-140 |
Overall Rating: /5.00
What We Like Most
- Achieved good results in our lab testing for contaminant reduction.
- Filtered water tasted and smelled 100% clean.
- Has certifications for 66 contaminants against NSF standards 42, 53, and 401.
- Fairly easy to set up, prime, use, and maintain.
- Fast flow from dedicated faucet.
- Simple, space-saving design.
- Very affordable up-front cost and below-average annual maintenance costs.
- 2-year (limited) warranty.
What We Don’t Like
- NSF certifications mostly limited to “easier-to-remove” organics.
- ½” feed water adapter (T-valve) didn’t fit our ⅜” supply, and no adapters were included.
- Parts are light plastic and feel pretty cheap, including the chrome faucet that’s actually plastic.
- No filter life indicator.
- 3rd-party customers complained about taste issues, leaking, and extremely slow faucet flow.
How the Culligan US-EZ-4 Compares to…
18 Other Under Sink Water Filters
In this video, Sara highlights our under sink water filter top picks. The Culligan US-EZ-4 was included in our testing, but didn’t make the cut.
Please note: Our full guide on the best under sink water filters is available here.
Video Chapters + Comparison Sheet
- Link to Comparison Sheet
- 00:00 – Intro
- 00:34 – How We Tested & Rated
- 01:53 – Our Recommendations
- 03:01 – Best Overall (Cloud RO)
- 15:11 – 2 Best Tankless ROs (Waterdrop G3P600 & X12)
- 27:26 – Best Non-RO Filter (Epic Smart Shield)
- 31:22 – Highest Filtration Score (Aquasana SmartFlow)
- 32:02 – Made in USA (USWS All American & Home Master TMHP-L)
- 32:34 – Budget RO Pick (APEC ROES-50 Essence)
- 32:51 – AO Smith AO-US-200 & Culligan US-EZ-4
- 33:34 – Summary
Full Analysis of the Culligan US-EZ-4
Filtration: /5.00
1. Lab Results: /5.00
Remember that our before vs after lab comparison is not an exact science. It’s informational and subject to variability, inaccuracies, and interferences caused by natural fluctuations in water quality, accidental contamination, human error, instrumentation issues, and more. Furthermore, our lab-testing is limited to those contaminants present in our water supplies and at their respective concentrations. As such, it can only give us a general idea for how effective a certain water treatment product might be.
Lab Results Chart
| Potentially Harmful | Aesthetic Issues | Feed Water Level | Filtered Water Level | Reduction Rate | |
| Water Disinfectants | |||||
| Chlorine (mg/L) | ✖ | ✖ | 1.22 | 0 | 100% |
| Disinfection Byproducts | |||||
| Bromodichloromethane (µg/l) | ✖ | 2.04 | 0 | 100% | |
| Bromoform (µg/l) | ✖ | 1.86 | 0 | 100% | |
| Dibromochloromethane (µg/l) | ✖ | 2.82 | 0 | 100% | |
| Chloroform (µg/l) | ✖ | 1.07 | 0 | 100% | |
| Metals | |||||
| Copper (mg/L) | ✖ | ✖ | 0.04 | 0 | 100% |
| Barium (mg/L) | ✖ | 0.04 | 0 | 100% | |
| Boron (mg/L) | ✖ | 0.06 | 0.03 | 50% | |
| Lithium (mg/L) | ✖ | 0.01 | 0 | 100% | |
| Strontium (mg/L) | ✖ | 0.42 | 0.22 | 48% | |
| Salts | |||||
| Nitrate (N) (mg/L) | ✖ | 1.96 | 0 | 100% | |
| Fluoride (mg/L) | ✖ | 0.58 | 0.57 | 2% | |
| Other | |||||
| Uranium (µg/L) | ✖ | 1 | 0 | 100% | |
| Impurities NOT Detected in Unfiltered Tap Water Sample | |||||
| Explanation: | |||||
| Full Removal | |||||
| Considerable Reduction | |||||
| Concentration More Than Double of Unfiltered Water Sample | |||||
| Potential Leaching Reached or Exceeded the Strictest Public Health Guideline We Could Find | |||||
*100% means reduction to below the minimum detection level. To learn more about our testing procedures check our editorial guidelines.
Link to Filtered Water Report
Link to Unfiltered Water Report
Usability: /5.00
Costs: /5.00
Please note: This page is still a work in progress. Additional content and details will be added shortly – stay tuned!
Further Reading
About the Author(s)
Sara has been a lifelong home-improvement fan (she’s been hooked on This Old House since she was five) and taught herself any project she didn’t already know by watching YouTube tutorials. She is also an award-winning filmmaker. Armed with this skillset, Sara installs, primes, samples, uses, and maintains nearly every point-of-use water treatment systems we test – then brings her results to life on camera for our YouTube channel.
Raoul has a background in mechanical engineering and has been writing about home water treatment since 2015. He designs our product review processes, analyzes the results, and ties everything together. As editor-in-chief, he tries hard to keep the whole operation running smoothly behind the scenes.