9 Best Under Sink Water Filter Systems (*Update 2024)
Written by: Alexandra Uta // Expert Fact-Checking: Buddhini Dolapihilla, MBSS // Last Updated: Jan 31, 2024
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Top Pick: What’s the Best Under Sink Water Filter?
The best under sink water filter in 2024 is the Clearly Filtered 3-Stage, because it is NSF-tested to remove 200+ contaminants, incredibly easy to install and maintain, durable, backed by a 30-day satisfaction guarantee and lifetime warranty, and it has a long filter life of 2,000 gallons.
There are numerous under sink water filters available for various purposes. Some are good, some bad, and with so many options finding the right system for your needs can be challenging.
To assist you in making an informed choice, we have thoroughly evaluated over 28 of the top under sink water filters currently on the market. Since the initial publication of this buying guide on March 1, 2021, we have dedicated countless hours to researching, reviewing, testing, comparing, and ranking these products. We have continuously updated and improved this guide to provide you with the most up-to-date information.
Contents
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No Time to Read? Check Our List of the Best Under Sink Water Filters!
| Model | Details | |
|---|---|---|
 Best Overall with Most Contaminants Removed: Clearly Filtered 3-Stage |
Overall Rating: 5.0/5.0 ⓘRatings based on effectiveness of filtration, NSF standards, life of filter elements, cost, our own testing, user ratings, product warranty and support, and other factors.
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Price: $$$ Type: 3-Stage Under Sink Water Filter, Inline Filter Life: 2,000 gal Testing & Certs: NSF 42, 53, 401 Annual Cost: $440 Read Review: Click Alexa’s Video Review: Click |
 Best System with Reverse Osmosis: Aquasana OptimH2O |
Overall Rating: 4.5/5.0 ⓘRatings based on effectiveness of filtration, NSF standards, life of filter elements, cost, our own testing, user ratings, product warranty and support, and other factors.
|
Price: $$ Type: RO System Filter Life: 365 gal Testing & Certs: NSF 42, 53, 58, 401, P473 Annual Cost: ~$240 Read Review: Click |
 Best for Tankless Under Sink RO Purification: Waterdrop G3 |
Overall Rating: 4.0/5.0 ⓘRatings based on effectiveness of filtration, NSF standards, life of filter elements, cost, our own testing, user ratings, product warranty and support, and other factors.
Get 5% Off on Top of Any Current Waterdrop Sale! Use Code: |
Price: $$$ Type: RO System Filter Life: 550-2,200 gal Testing & Certs: NSF 58, 372 Annual Cost: ~$145 Read Review: Click Sara’s Video Review: Click |
 Best Budget Option: Epic Smart Shield |
Overall Rating: 4.5/5.0 ⓘRatings based on effectiveness of filtration, NSF standards, life of filter elements, cost, our own testing, user ratings, product warranty and support, and other factors.
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Price: $ Type: Single-Stage, Inline Filter Life: 651 gal Testing & Certs: NSF 42, 53, 401 Annual Cost: $115 Read Review: Click Alexa’s Video Review: Click |
Under Sink Water Filter Reviews
Our Top Picks
- Clearly Filtered 3-Stage – Best Overall
- Aquasana OptimH2O – Best for RO Purification
- Waterdrop G3 – Best for Tankless RO Purification
- Epic Smart Shield – Best Budget Option
- Crystal Quest 1000C & 1000CP – Best for Well Water
- Aquasana AQ-5300+ Max Flow
- Culligan US-EZ-1 vs. US-EZ-3 vs. US-EZ-4 – Best for Customization
- CuZn UC-200 – Highest Filtration Capacity
- Woder Advanced WD-G4-DC
1. Best Overall: Clearly Filtered 3-Stage
In our opinion, the best under sink water filter in 2024 is the Clearly Filtered 3-Stage. It has been repeatedly tested to remove/reduce well over 200 different water contaminants which is simply outstanding, especially for an under sink water filtration system that doesn’t apply reverse osmosis (RO).
Installation and maintenance are a piece of cake, and users are highly satisfied with their purchase. 5 stars!
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Clearly Filtered 3-Stage Under Sink Water Filtration System |
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| Price: | $$$ |
| Filter Type: | Inline |
| Filtration Capacity: | 2,000 gal |
| Testing: | NSF 42, 53, 401 |
| Annually: | $440 |
|
Overall Rating: 5.0/5.0 ⓘRatings based on effectiveness of filtration, NSF standards, life of filter elements, cost, our own testing, user ratings, product warranty and support, and other factors.
Get 10% Off! Use Code: |
|
Alexa’s Video Review
As part of the BOS team, Alexa has installed and tested the Clearly Filtered Under-the-Sink Water Filter System in her own home and with her own hands. She has used the system for several weeks to gather genuine first-hand experience. And most importantly, Alexa has documented the entire process, including her findings and personal opinion, in the video below:
Other Specs
- Model: 3-Stage Under the Sink Water Filter System
- Last Price: $550
- Filter Media: Activated Carbon + Proprietary Blend
- Filter Stages: 3
- WxHxD: 15″x15.4″x3.1″
- Fitting: ⅜”
- Warranty: Limited Lifetime
Key Features & Pros
- Built in the USA!
- 3-stage filtration process:
- Coconut shell granular activated carbon filter removes chlorine (98.6%), chloramines (95.3%), taste, odor, cloudiness and colors, and volatile organic compounds and other common chemicals. Made in USA!
- Special filter media blend reduces heavy metals like lead (98.9%) and chromium-6 (99.4%), pesticides, PFAS, radiological elements and more. Made in USA!
- Last filter stage focuses on fluoride (90.7%) and arsenic (94.3%).
- System is tested against NSF International standards 42, 53, and 401 for 230+ contaminants.
- Some of the most thorough testing we have ever seen.
- Healthy minerals are retained in the drinking water adding to your daily nutritional intake.
- Inline system works with your existing faucet.
- Features stainless steel inlet and outlet hoses for durability.
- Easy to install. Non-permanent setup – ideal for renters – shouldn’t take more than 10 to 15 minutes.
- Filters are modular, meaning they’re quick and easy to change without tools about once a year.
- High capacity: 2,000 gallons.
- Thanks to 30-day worry free trial, you can send back the under sink system for a full refund.
- Limited lifetime warranty.
Cons
- Expect 25 to 35 percent reduced water pressure.
- High quality + domestic manufacturing mean relatively high price compared to some of the competition.
- Replacements filters aren’t exactly cheap either. At least you can subscribe to Clearly Filtered’s VIP Program for 10% discount and free shipping.
Our Rating
- Filtration Performance: 5.0/5.0
- Filter Life: 5.0/5.0
- Price: 4.0/5.0
- Maintenance Cost: 4.5/5.0
- Overall: 5.0/5.0
Best for
The Clearly Filtered 3-Stage system is best for people who want an under sink drinking water filter that’s compact, easy to connect and use, and highly effective.
2. Best for Under Sink Reverse Osmosis Water Purification: Aquasana OptimH2O
In our opinion, the number one tank-based under sink reverse osmosis system in 2024 is the OptimH2O by Aquasana. Why? Because it’s highly effective at reducing dozens of harmful contaminants from water and, at the same time, it remineralizes the filtered water with healthy calcium, magnesium, and potassium. This improves the taste of the water and balances its pH. All in all, an excellent offer. 4.5 stars!
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Aquasana OptimH2O Reverse Osmosis Water Filtration System |
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| Price: | $$ |
| Filter Type: | RO System, Dedicated Faucet |
| Filtration Capacity: | 365 gal |
| Certifications: | NSF 42, 53, 58, 401, P473 |
| Annually: | ~$240 |
|
Overall Rating: 4.5/5.0 ⓘRatings based on effectiveness of filtration, NSF standards, life of filter elements, cost, our own testing, user ratings, product warranty and support, and other factors.
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Other Specs
- Model: OptimH2O
- Filter Media: Activated Carbon, RO Membrane, Activated + Catalytic Carbon + Ion Exchange Resin, Remineralization
- Filter Stages: 4
- Membrane Rating: 35 gpd
- Recovery Rate: 29.43%
- WxHxD (System): 12″x12.5″x4.5″
- Tank: 11″x16″x11″, 3.2 gal
- Water Temperature: 40-100 °F
- Operating Pressure: 40-100 psi
- Warranty: 2 Years
Key Features & Pros
- Good price. Most people are more than happy with their purchase.
- Choose from 3 faucet designs: Chrome, oil-rubbed bronze, and brushed nickel.
- NSF certified to filter chlorine + chloramines (97.66%), mercury (>95.8%), lead (99.3%), arsenic 5 (97.6%), volatile organic compounds (~99.4%), chromium 6 (97.0%), fluoride (95.7%), and several other substances.
- Standards 42, 53, 58, 401, P473.
- Uses 3 filter stages:
- Activated carbon filter adsorbs chlorine and larger particulates.
- Reverse osmosis membrane rejects microorganisms, heavy metals, etc.
- Claryum filter (activated + catalytic carbon + ion exchange resin) eliminates pesticides, any remaining water disinfectants, a bunch of heavy metals, and more.
- Remineralizer adds healthy minerals back into water which were removed in RO purification process.
- System is suited for DIY installation. All parts are included in the package.
- Simply follow step-by-step instructions. If you’re stuck, reach out to Aquasana’s helpful customer service.
- Maintenance doesn’t require much time or effort.
- Entire filter system is warranted for 2 years.
- 90-day satisfaction policy guarantees peace of mind.
Cons
- Issues with leaking and overall quality.
- Flow rate is not exactly fast.
- Produces wastewater like all other reverse osmosis systems.
- Average annual filter replacement cost totals to about $240, depending on your water use and water quality.
- Not one of the cheapest RO systems to maintain, but still acceptable considering performance.
- Join filter subscription program for discounts.
Our Rating
- Filtration Performance: 5.0/5.0
- Filter Life: 4.5/5.0
- Price: 4.0/5.0
- Maintenance Cost: 4.0/5.0
- Overall: 4.5/5.0
Best for
The Aquasana OptimH2O is best for people looking for an under sink reverse osmosis system that’s easy to install and maintain, NSF-certified for contaminant removal, and that provides slightly alkaline drinking water.
3. Best for Tankless RO Purification: Waterdrop G3 Under Sink Water Filter System
If you lack the necessary space under your kitchen sink, we have the ideal solution for you: The Waterdrop G3 tankless under sink reverse osmosis system. Because the system filters on demand it doesn’t need a water storage tank which saves a fair bit of space in your sink cabinet.
Plus, it makes the installation even simpler. This in addition to great drinking water taste are worth four stars from us.
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Waterdrop Tankless Under Sink RO System |
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| Price: | $$$ |
| Filter Type: | RO System, Own Faucet |
| Filtration Capacity: | 550-2,200 gal |
| Certifications: | NSF 58, 372 |
| Annually: | ~$145 |
|
Overall Rating: 4.0/5.0 ⓘRatings based on effectiveness of filtration, NSF standards, life of filter elements, cost, our own testing, user ratings, product warranty and support, and other factors.
Get 5% Off on Top of Any Current Waterdrop Sale! Use Code: |
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Sara’s Video Review
Being part of the BOS team, Sara has ordered and tested the Waterdrop G3 Reverse Osmosis System, which means she has installed the system with her own hands and used it for several weeks for some genuine first-hand experience! Sara has documented the entire process, including her findings and personal verdict, in the video provided below:
Other Specs
- Model: G3P600
- Last Price: $539.00
- Filter Media: Sediment + Carbon Composite, RO Membrane, Carbon Block
- Filter Stages: 4
- Flow Rate: 0.42 gpm
- Membrane Rating: 600 gpd
- Recovery Rate: 66%
- WxHxD: 5.67″x17.72″x18.12″
- Water Temperature: 41-100 °F
- Operating Pressure: 14.5-87 psi
- Warranty: 1 Year
Key Features & Pros
- Space-saving tankless design.
- 4 filter stages:
- Composite filter (sediment + activated carbon) traps chlorine and sediments.
- RO membrane rejects bacteria, even smaller viruses, and heavy metals among other things.
- Activated carbon block post-filter removes any residual tastes and chemicals.
- NSF certified for the rejection of total dissolved solids (TDS).
- System has built-in pressure pump for higher flow rate of around 0.4 gpm.
- Quickly fills a large container with ease. One cup in about 8 seconds.
- Also reduces water waste from 3-5 gallons to 0.67 gallon for every gallon filtered.
- BPA-free materials only.
- Easy installation shouldn’t take more than one or two hours.
- Smart LED faucet indicates filter status. White light: Filters are still good. Yellow light: Less than 40 gallons of filtered water left. Red light + beeping sound: Change filters immediately.
- Similar lights are found on system front panel.
- Makes timely filter changes much easier.
- Front panel + faucet also show permeate water TDS which is another indicator for filter status.
- Filter change takes virtually 10 seconds – tools-free and no need to shut off feed water. Yearly cost: About $145.
- Leak protection.
- Waterdrop offers 30-day money-back guarantee.
- One-year warranty.
Cons
- We’re missing specific reduction rates for more contaminants.
- Some people need to drain a full gallon of clean water until system front panel shows optimum TDS. This phenomenon is known as TDS creep.
Our Rating
- Filtration Performance: 4.0/5.0
- Filter Life: 5.0/5.0
- Price: 3.5/5.0
- Maintenance Cost: 4.0/5.0
- Overall: 4.0/5.0
Best for
The Waterdrop G3 is best for people who want a tankless under sink RO system that’s small, easy to use, and fast.
4. Best Budget Option: Epic Smart Shield Inline Under Sink Water Filter by Epic Water Filters
The Epic Smart Shield is a non-RO (reverse osmosis) under sink filter system perfect for tap water and well water. It’s certified to remove contaminants including lead, chlorine/chloramine, asbestos, cyst, E. Coli, and many other. Furthermore, it’s surprisingly affordable especially when compared to the Clearly Filtered 3-Stage under sink water system reviewed above and users love the great taste of the purified water. 4.5 stars!
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Epic Smart Shield Undersink Water Filter |
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| Price: | $ |
| Filter: | Inline |
| Filtration Capacity: | 651 gal |
| Certifications: | NSF 42, 53, 401 |
| Annually: | $115 |
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Overall Rating: 4.5/5.0 ⓘRatings based on effectiveness of filtration, NSF standards, life of filter elements, cost, our own testing, user ratings, product warranty and support, and other factors.
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Alexa’s Video Review
Being an integral member of the BOS team, Alexa has ordered and tested the Epic Smart Shield Under Sink Water Filter at home. She shares her hands-on experience of installing and using the system in the video below:
Other Specs
- Model: Epic Smart Shield
- Last Price: $135.00
- Filter Media: Carbon Block
- Flow Rate: 1.25 gpm
- WxHxD: 4.25″x19.75″x4.5″
- Water Temperature: 33-100 °F
- Operating Pressure: 40-120 psi
- Warranty: Lifetime
Key Features & Pros
- Great for people on a tight budget!
- Everything is made in USA.
- Designed for both municipal water and well water.
- Areas with high sediment levels and people on well water are recommended to use additional 5-micron Epic Smart Shield sediment pre-filter to prolong filter life of Epic Smart Shield.
- Removes more than 70 contaminants that might be lurking in your water.
- NSF certified against standards 42, 53, and 401 for chlorine taste and odor (95.5%), particulates, chloramine (95.5%), cyst (>99.99%), lead (>99.3%), VOC (99.6%), asbestos (>99%), mercury (>96.6%), MTBE, turbidity, bisphenol A, Estrone, Ibuprofen, Naproxen, Nonyl phenol, Phenytoin, and more.
- Also tested for removal of E. Coli + Pseudomonoas Aeruginosa, PFOA + PFOS, microplastics, radiological elements, and several other.
- Based on activated coconut carbon block filtration.
- Very easy to install. Shouldn’t take more than 20 minutes even if you don’t have any prior plumbing experience due to inline design and quick-connect fittings.
- Installation kit included (e.g. connector hoses, feed water adapter).
- Inline meaning works with your existing faucet. But you can also purchase dedicated polished-chrome faucet kit.
- Average filter capacity is 12 months (around 650 gallons purified water). Annual cost: $115 which seems fair.
- Join Clean Water Club and save 20% on replacement filters.
- Filters are recyclable through company’s own recycling program. Collect 3 and mail them back to get a free filter as reward.
- Great customer support, lifetime warranty, and return policy.
Cons
- Flow rate is 1.25 gallons per minute (gpm), so you might see water pressure drop.
Our Rating
- Filtration Performance: 4.5/5.0
- Filter Life: 4.0/5.0
- Price: 5.0/5.0
- Maintenance Cost: 5.0/5.0
- Overall: 4.5/5.0
Best for
The Epic Smart Shield is by far the best budget under sink water filter.
→ Detailed Epic Smart Shield Review
5. Best for Well Water: Crystal Quest 1000C & 1000CP Under Sink Filter Systems
Crystal Quest’s 1000C and 1000CP are great RO under sink filters for people on well water.
Side note: The only difference between the two is the latter comes with an electronic pump to boost water pressure.
With 12 filtration stages, both systems are capable of eliminating all contaminants commonly found in wells and many more.
And if you want you can add a 13th filter stage (UV light) on top for 99.99% reduction of microorganisms – think bacteria, viruses, and protozoa. This turns the Crystal Quest 1000C into the 3000C, and the 1000CP into the 3000CP.
Crystal Quest 1000C |
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| Price: | $$ |
| Filter Type: | RO System, Separate Faucet |
| Filtering Capacity: | 1-3 Years |
| Certifications: | – |
| Annually: | ~$100-155 |
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Overall Rating: 4.5/5.0 ⓘRatings based on effectiveness of filtration, NSF standards, life of filter elements, cost, our own testing, user ratings, product warranty and support, and other factors.
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Other Specs
- Model: 1000C
- Last Price: $298.40
- Filter Media: Carbon Block, 0.02-Micron UF Membrane, GAC, Ion Exchange, KDF, RO, GAC, Sediment Filter Pads
- Filter Stages: 12
- Flow Rate: 0.03 gpm
- Membrane Rating: 50 gpd
- WxHxD: 16″x21″x8″
- Tank: 11″x15″x11″, 3.2 gal
- Water Temperature: 40-85 °F
- Operating Pressure: 30-60 psi
- Warranty: 1 Year
Key Features & Pros
- 12 stages of filtration remove sediments, water disinfectants, pesticides, herbicides, industrial solvents, VOCs, PCBs, microorganisms, taste, odor, heavy metals like iron, hardness, rotten egg smell, and much more.
- Filter stage 1: Activated carbon block, 5-micron nominal. Adsorbs chlorine and all kinds of chemicals. Also traps undissolved matter to protect the rest of the system from fouling.
- Filter 2: Ultrafiltration membrane, 0.02-micron. Reduces microorganisms and large organic/inorganics.
- Filter 4: Granular activated carbon. Removes 99.9% chlorine taste and smell, and a bunch of chemicals.
- Filter 5: Ion exchange resin. Targets metals and water hardness.
- Filter stage 6 & 7: Eagle Redox Alloy media (copper-zinc blend). Removes hydrogen sulfide, chromium, cadmium iron, mercury, and other dissolved metals. Also prevents bacterial growth.
- Stage 9: RO membrane. Rejects anything larger than 0.0001 micron.
- Filter 11: GAC filter to remove residual taste.
- Stages 3, 8, 10, and 12 are 1-micron filter pads. They remove suspended particles.
- Filter 13 (optional): UV light treatment. Inactivates bacteria, viruses, and protozoa.
- Water production is sufficient for a larger home.
- Standard under sink installation.
- Maintenance needs are minimal. Cost for replacement filters: $100-155 per year.
- You can subscribe to get 5% off.
- One-year warranty (limited).
Cons
- Installations instructions could do with more details.
- We miss NSF testing.
- Water hardness shouldn’t exceed 15 grains per gallon, iron content 2 ppm. Otherwise, filters tend to clog early.
Our Rating
- Filtration Performance: 4.0/5.0
- Filter Life: 5.0/5.0
- Price: 5.0/5.0
- Maintenance Cost: 4.5/5.0
- Overall: 4.5/5.0
Best for
These under sink water filters by Crystal Quest are best for heavily contaminated well water.
6. Aquasana AQ-5300+ Max Flow Under Counter Water Filter
The Aquasana Claryum 3-Stage Under Sink Water Filter aka Aquasana AQ-5300+ Max Flow combines activated with catalytic carbon filter media + ion exchange resin to effectively remove/reduce a wide range of common tap water contaminants.
Aquasana AQ-5300+ Under Sink Water Filtration System |
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| Price: | $$ |
| Filter Type: | Extra Faucet |
| Filtration Capacity: | 800 gal |
| Certifications: | NSF 42, 53, 401, P473 |
| Annually: | ~$160 |
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Overall Rating: 4.0/5.0 ⓘRatings based on effectiveness of filtration, NSF standards, life of filter elements, cost, our own testing, user ratings, product warranty and support, and other factors.
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Gallery
Other Specs
- Model: AQ-5300+
- Last Price: $224.99
- Filter Media: 20-Micron Sediment Pre, Activated Carbon, Catalytic Carbon, Ion Exchange Resin, Submicron Filtration
- Filter Stages: 3
- Flow Rate: 0.72 gpm
- WxHxD: 12″x12.85″x4.25″
- Water Temperature: 40-90 °F
- Operating Pressure: 20-80 psi
- Fitting: 3/8″
- Warranty: 1 Year
Key Features & Pros
- High customer satisfaction. Most would buy again and recommend to friends & family.
- Under sink filter can reduce up to 99% of 77 contaminants, including chlorine and chloramine, cysts, lead, BPA, pharmaceuticals, and VOCs.
- According to NSF/ANSI standard certifications 42, 53, 401, and protocol P473.
- You have the choice between 3 faucet designs to match your kitchen décor.
- System installation is easy. All necessary parts are included and the manufacturer instructions are precise (installation videos on YouTube!). No need to hire a professional plumber and spend a few hundred extra bucks.
- Replace filters when they’ve reached their capacity limit (800 gallons) or every 6 months, whichever comes first.
- Filter life isn’t exceptional but still okay.
- No need to shut off water supply thanks to clever filter design.
- You’ll hear acoustic alarm and see red light flashing after 6 months. Takes out any guesswork.
- Covered by one-year limited warranty.
- Customer service is reliable.
Cons
- Reported problems with tubing popping out, broken filter housings, flimsy faucets, and failing O-rings.
- May cause leakage.
- Some reviewers complained about water pressure being way too slow.
Our Rating
- Filtration Performance: 4.0/5.0
- Filter Life: 4.0/5.0
- Price: 5.0/5.0
- Maintenance Cost: 5.0/5.0
- Overall: 4.0/5.0
Best for
This Aquasana under sink filter is best for NSF-certified contaminant reduction achieved through multi-stage filtration (non-RO).
7. Best Customizable: Culligan US-EZ-1 vs. US-EZ-3 vs. US-EZ-4 Under Sink Filters
Just like Aquasana, Culligan provides three under sink water filtration systems with a single interchangeable filter cartridge each: The US-EZ-1 (or Easy-Change 1), the US-EZ-3, and the US-EZ-4. The reason why we decided to review them is they are relatively low-cost and therefore suited for people on a tight budget.
Where’s the difference between the US-EZ-1, 3, and 4? In a nutshell, the US-EZ-1 provides basic chlorine filtration only. The US-EZ-3 is more advanced. And the US-EZ-4 is certainly the most sophisticated under sink water filter system of the 3 providing “premium” filtration.
All things considered, we wouldn’t recommend the US-EZ-1 unless you already have really good water and are only concerned about taste issues. Thus 3 stars. The US-EZ-3 is okay, we’ll award 3.5 stars. But we would only really recommend the US-EZ-4 to most of our readers. 4 stars!
Culligan US-EZ-4 |
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| Price: | $ |
| Filter: | Extra Faucet |
| Filtration Capacity: | 500 gal |
| Certifications: | NSF 42 + 53 + 401 |
| Annually: | ~$160 |
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Overall Rating: 4.0/5.0 ⓘRatings based on effectiveness of filtration, NSF standards, life of filter elements, cost, our own testing, user ratings, product warranty and support, and other factors.
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Other Specs
- Model: US-EZ-4
- Filter Media: Carbon-Based
- Flow Rate: 0.5 gpm
- WxHxD: 3.5″x14.325″x3.5″
- Water Temperature: 40-100 °F
- Operating Pressure: 30-100 psi
- Warranty: 2 Years
Key Features & Pros
- Compact design.
- Carbon-based filtration.
- Basic filter is tested and certified to remove chlorine taste & odor and particulates (Class III).
- Advanced filter eliminates chlorine, particulates (Class I), as well as cysts, turbidity, lead, lindane, and atrazine (NSF 42 + 53).
- The premium filter takes care of chlorine AND chloramines – more information here and in this guide – particulates (Class I), cysts, lead, mercury, VOCs, MTBE, PFOA/PFOS, and turbidity among a few other things (NSF 42 + 53 + 401).
- Separate lead-free faucet included.
- Quick connect fittings and detailed DIY instructions make installing to cold water line straightforward with no need for calling a plumber.
- Modular twist on/off filters were designed for convenience and can be replaced in mere minutes and without turning off the feed water supply.
- US-EZ-1 lasts up to 3,000 gallons of water or 12 months. Annual cost: $20. What?!
- US-EZ-3 is good for 500 gallons or six months. About $90 annually. Still incredibly affordable.
- US-EZ-4 is also rated at 500 gallons or six months filtration capacity. Around $160 per year for replacement filters is within the normal range.
- Everything is backed by a limited manufacturer warranty for 2 years.
Cons
- 0.5 gpm at 60 psi is a little low.
- The included dispenser is made from cheap plastic except for its metal spout, so don’t expect mind-blowing quality.
- Problems with leaking units mainly due to bad plastic connectors and cracked filter housings.
Our Rating
- Filtration Performance: 4.0/5.0
- Filter Life: 4.0/5.0
- Price: 5.0/5.0
- Maintenance Cost: 4.0/5.0
- Overall: 4.0/5.0
Best for
Culligan’s under sink filtration systems are best for customization. You can switch between the different cartridges.
→ Full Review of Culligan’s Under Sink Water Filters
8. Best for Zero Maintenance: CuZn UC-200 Under Counter Water Filter
Next on our list: The CuZn UC-200 inline water filter.
Water is supposed to be almost tasteless. If that’s what you are looking for and your water doesn’t contain certain contaminants that the CuZn under sink filter can’t handle, consider giving it a shot. You can’t really go wrong – remember: If you don’t like what you receive, claim the guarantee.
CuZn UC-200 Under Counter Water Filter |
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| Price: | $ |
| Filter: | Inline |
| Filtration Capacity: | 50,000 Gallons |
| Testing: | NSF 42 |
| Annually: | – |
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Overall Rating: 3.0/5.0 ⓘRatings based on effectiveness of filtration, NSF standards, life of filter elements, cost, our own testing, user ratings, product warranty and support, and other factors.
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Other Specs
- Model: CuZn UC-200 Series
- Filter Media: Sediment Membranes, GAC, KDF-55
- Flow Rate: 2 gpm
- WxHxD: 4.5″x15.5″x4.5″
- Water Temperature: Up to 110 °F
- Operating Pressure: Up to 80 psi
- Warranty: 5 Years
Key Features & Pros
- Under counter water filter is manufactured in the USA which is quite rare nowadays.
- It’s bacteriostatic – meaning there’s almost no chance that bacteria or mold will grow inside the unit. This is a great benefit over regular carbon filters.
- 3-stage filtration: Combines micro sediment membranes with granular activated carbon and KDF-55. Say goodbye to a range of organic and inorganic contaminants including chlorine, lead, herbicides, pesticides among others (not fluoride, sorry).
- Filter media is NSF tested against Standard 42.
- Healthy minerals like calcium and magnesium are left untouched. This is good for your health, but bad for your coffee maker.
- Filter installation process is a breeze and will only take you a few minutes thanks to the simple design. If you don’t know how, CuZn provides a video with step-by-step instructions on their website.
- 3/8″ fittings are included. For non-standard plumbing, CuZn usually sends a special installation kit with everything you need for free, so make sure to reach out to them.
- No cartridge replacements required – simply set up the filter and forget about it for the next couple of years. Once the filter has reached the end of its lifespan you have to replace the entire unit.
- 5 years warranty and 90 days satisfaction guarantee are part of the deal. If you don’t like how the filter performs, just send it back and get a full refund.
Cons
- Theoretically, you get a capacity of 50,000 gallons or an equivalent of 5 years, whichever comes first. But it always depends on feed water quality. Just like most other under sink filter systems, the CuZn cannot handle hard water very well – one of the reasons to use it with tap water if possible. Also, we highly doubt that the activated carbon will do much even after 1 or 2 years of use.
- Some customers struggled with leaks, for example at the case of the unit. We also read about black grains that someone found in his water.
- The good news: CuZn’s customer service is extremely responsive and helpful. The team is willing to take on any problem that users might have with the under sink filter.
Our Rating
- Filtration Performance: 3.0/5.0
- Filter Life: 5.0/5.0
- Price: 3.5/5.0
- Maintenance Cost: 5.0/5.0
- Overall: 3.0/5.0
Best for
Due to 50,000 gallons filter life, the CuZn UC-200 is best if you want a low-maintenance under sink filter system.
→ See the Full CuZn UC-200 Review Here
9. Woder Advanced WD-G4-DC Under Sink Water Filter
Our last review features the Woder Advanced WD-G4-DC Under Sink Water Filter. It’s an inline system that is also affordable and has a high flow rate. But is it really worth considering?
Woder Advanced WD-G4-DC Inline Water Filtration System |
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| Price: | $ |
| Filter: | Inline |
| Filtration Capacity: | 8,480 gal |
| Certifications: | – |
| Annually: | ~$60-120 |
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Overall Rating: 3.0/5.0 ⓘRatings based on effectiveness of filtration, NSF standards, life of filter elements, cost, our own testing, user ratings, product warranty and support, and other factors.
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Other Specs
- Model: Advanced WD-G4-DC
- Filter Media: Not Specified
- Flow Rate: 2 gpm
- WxHxD: 15.4″x 3.6″x2.52
- Fitting: ⅜”
- Warranty: 1 Year
Pros
- Affordable!
- The Woder Advanced WD-G4-DC has a single filter stage. It’s claimed to remove heavy metals such as lead and chromium 6, PFAS, VOCs, chlorine, sediments, and other harmful contaminants.
- Also improves water taste and odor.
- Flow rate is 2 gallons per minute which is definitely enough for use on your kitchen sink.
- Installation is simple thanks to the under sink water filter being inline.
- Uses durable stainless steel hoses.
- The Woder is also easy to maintain. There’s a built-in shut off valve. Cost for replacement filters: Around $60 to $120 annually, which is cheap!
- System is backed by a 1-year warranty and 60 days satisfaction guarantee.
Cons
- The company says the Woder Advanced WD-G4-DC has a filter life of 8,480 gallons. We find this hard to believe.
- We don’t know the exact type of filter media. It is not disclosed by Woder.
- We miss lab reports about NSF testing or certifications.
- Some users complained about leaks and slowing water flow.
Our Rating
- Filtration Performance: 3.0/5.0
- Filter Life: 4.0/5.0
- Price: 5.0/5.0
- Maintenance Cost: 5.0/5.0
- Overall: 3.0/5.0
Best for
Without knowing further details, the Advanced WD-G4-DC under sink water filter by Woder is best used for basic tap water treatment to improve taste and odor.
More Reviews:
Comparison List
(Mobile Hint: Swipe to Scroll)
| Filter Systems | Price | Type | Process | Stages | Capacity | NSF | Annually | Warranty | Additional Info |
|---|---|---|---|---|---|---|---|---|---|
| Clearly Filtered 3-Stage System | $$$ | Inline | Activated Carbon + Proprietary Blend | 3 | 2,000 gal | 42, 53, 401 | $440 | Limited Lifetime | |
| Aquasana OptimH2O Undersink Filter | $$ | RO | Activated + Catalytic Carbon, RO, Ion Exchange Resin, Remineralizer | 4 | 365 gal | 42, 53, 58, 401, P473 | ~$240 | 2 Years | |
| Waterdrop G3 | $$$ | RO | Sediment + Carbon Composite, RO, Carbon Block | 4 | 550-2,200 gal | 58, 372 | ~$145 | 1 Year | |
| Epic Smart Shield Undersink Filter | $ | Inline | Carbon Block | 1 | 651 gal | 42, 53, 401 | $115 | Lifetime | |
| Crystal Quest 1000C & 1000CP | $$ | RO | Carbon Block, UF, GAC, Ion Exchange, KDF, RO, GAC, Sediment | 12 | 1-3 Years | – | ~$100-155 | 1 Year | |
| Aquasana AQ-5300+ | $$ | Separate Faucet | Sediment Pre-Filter (20 Microns), Activated + Catalytic Carbon, Ion Exchange, Submicron Filtration | 3 | 800 gal | 42, 53, 401, P473 | $160 | 1 Year | |
| Culligan US-EZ-4 | $ | Extra Faucet | Carbon | 1 | 500 gal | 42, 53 | ~$160 | 2 Years | |
| CuZn UC-200 | $ | Inline | Sediment, GAC, KDF-55 | 1 | 50,000 gal | 42 | – | 5 Years | |
| Woder Advanced WD-G4-DC | $ | Inline | ? | 1 | 8,480 gal | – | ~$60-120 | 1 Year |
Buying Guide: How to Choose the Under Sink Filter That’s Best for You
The following are key features worth considering when shopping for a high quality water filter system to install under your kitchen counter. They will help you choose the right one for your needs and budget.
Certifications
Almost every water filter does a great job at reducing chlorine and improving overall water aesthetics, which is a good start. But what about the really bad stuff, say some heavy metals and pesticides for example?
Truth is, not all water filters are created equal. When directly compared, some are way more effective at filtering certain kinds of contaminants than others. Thus, there are big differences in the level of water purity they can provide.
By checking for important NSF/ANSI certifications, you can make sure that a certain filter or filter system is able to remove all or at least the majority of harmful substances your water may contain. What certifications to focus on? Standard 42, 53, 401 and 58 (RO systems only).
Filtration Technology
There is carbon filtration, there is reverse osmosis (RO), there is ion exchange. Different water filters use different technologies and media to help you get rid of impurities in your water. And while reverse osmosis units produce the best possible results, it might be more efficient for your water conditions to install a filter that’s much more simple.
Usually, the best approach is to test your water as a first step. As soon as you know what you are facing, you can go out and find an appropriate filter.
Filter Stages
Although there are exceptions, the general rule is that the more filter stages a system has, the higher is the quality of treated water it provides.
The downside is that the more stages, the higher maintenance costs and the bulkier the filter system.
Flow Rate & Water Pressure
Non-RO under sink water filtration systems don’t come with a storage tank. So the water gets filtered on demand. The thing is, nothing is more annoying than having to wait a whole day to fill a single glass of drinking water. #exaggerate
But seriously, pay attention to water flow rates measured in gallons per minute (gpm). Besides, low flow also means low water pressure.
A standard kitchen faucet that has no water filter attached to it delivers somewhere around 2.0 gpm (Source). The lowest flow rate we could find with an under sink filtration system was 0.25 gpm.
Meanwhile, you should note that thorough filtration requires time. This is why the Aquasana AQ-5300+ for example, which features very sophisticated filtration technology, provides no more than 0.72 gallons of water per minute.
Under Sink Water Filter Installation
When you can actually install a home water filter system yourself, you save quite a bit by not having to call a plumber. The good news is that most under sink purifiers fall under this category – even if you don’t have any prior experience. Some don’t even require the use of tools, except maybe for an adjustable wrench to tighten the fixings.
If a filter comes with a separate faucet rather than featuring an in-line design, the installation process can be more difficult, but not too much. For this type, you will have to drill an extra hole somewhere in your counter in case your kitchen sink doesn’t have a spare one.
By the way, the advantage of using a separate faucet is that you don’t have to purify every drop of water you use. Only water used for direct consumption gets filtered. This will help you to save time and money in the long run. How? It’s simple: Your filters are going to last way longer. On the other hand, if all the water is being processed, the filters will reach their capacity a lot sooner.
Maintenance & Filtration Capacity
One of the main benefits of under sink water filters is that they are easy to maintain, so less for you to worry about. The reason is that the amount of water gallons that a filter cartridge can handle before it needs replacement is relatively high.
One of the filters we reviewed above has a really high capacity of 50k gallons. If your household uses 3 gallons of filtered water per day, 50,000 will last you for more than 45 years – at least in theory. Because water filters are also limited by how long you can use them. This is due to the fact that bacteria might grow inside the filter media after months or years of use.
Also, keep in mind that filtration capacities are ideal values. Depending on the conditions in your home, such as feed water quality, a filter might never actually reach that benchmark.
The amount of work required to maintain a water filter system also depends on how well it was designed. Twist on/off filters can be changed in under 2 minutes. Filters with housings can be a pain in the a**.
Space
Some under counter water filters are larger than you’d think. If you have unlimited space in your sink cabinet, this doesn’t really matter. However, if you don’t, this should influence your final buying decision.
Also, don’t forget that reverse osmosis water filter systems use their own storage tank.
Under Sink Water Filter Costs
In terms of costs, you have to take into account the initial purchase plus recurring expenses for replacement cartridges, which start to add up in the long term. This is when high filtration capacities with fewer changes really pay off.
In all our under sink water filter reviews, we also estimated annual filter replacement cost for each system.
More on Under Sink Water Filters
What Exactly Is an Under Sink Water Filter?
An under sink water filter is a piece of equipment that can be used to purify the water at a single outlet in the home, usually the kitchen sink.
Under sink water filters are made of one or more filter stages that can use a variety of filter media. Most common is activated carbon, but there’s also ion-exchange resin, KDF, reverse osmosis membranes, catalytic carbon, sediment filters, and a few other.
The greatest benefits of installing an under sink filter in your home is improved water quality – ideal if you’re facing excessive chlorine, lead, or PFAS for example.
Generally speaking, under sink filters are easier to install and maintain than you might think. And they’re affordable, too! So, what are you waiting for?
The Different Types of Under Sink Water Filters and How They Work
In this section, we’ll briefly explain how an under counter water filter works, which isn’t overly complicated:
Inline vs. Dedicated Faucet
First of all, we need to differentiate between inline filters and those that come with a separate faucet.
- As the name suggests, inline under sink water filters are installed in line, meaning they’re added to the existing cold water line of your kitchen sink. When you open the kitchen faucet, the unfiltered feed water has to flow through the filter system before it comes out all nice and clean. Water is filtered on demand.
- Under sink filter systems with a dedicated faucet connect to the cold feed water valve, too, but from there they use their tubing to deliver the water. Many systems even come with their own storage tank to eliminate long waiting times.
Simple Under Sink Water Filters
Simple under sink water filters feature just one stage of filtration. This could mean that the water treatment process isn’t very thorough, but it doesn’t have to. Some water filter systems in this category, such as the Epic Smart Shield, work just fine and are very well capable of filtering the majority of a whole arsenal of contaminants from water.
Conventional Under Sink Units (Multi-Stage)
Conventional under sink systems with two or more filters usually combine a sediment filter, which traps dirt, rust, sand and other larger particles, with carbon filtration. The latter can be granular carbon or one or more carbon block filters. Activated carbon is great for neutralizing bad tastes and odors, and also to adsorb chemicals like chlorine and VOCs.
If you’re dealing with heavy metals you should consider a filter using KDF or anion exchange media.
RO Systems
Most reverse osmosis drinking water systems get installed under the kitchen sink, so we decided to include them in our reviews and buying guide. There are a few differences when compared to regular under sink water filter systems:
- Under sink RO systems feature either a pressurized water storage tank or an electric water pressure pump, or both.
- They come with their own faucet.
- They require a drain connection. This is because reverse osmosis water filtration always produces wastewater, no matter how efficient the process.
Who Should Buy an Undersink Water Filter?
Honestly, anyone who’s having tap or well water quality issues should consider buying an undersink water filter.
If your water smells or tastes unpleasant, there’s an under sink filtration system for that.
If your water is contaminated with lead, there’s a filter for that.
If your water contains pesticides due to agricultural runoff, there’s a filter option…
How to Install an Under Sink Water Filter
Don’t worry, under sink water filter system installation is nowhere near as difficult as installing a whole house filter system. What’s more, in most cases you don’t have to make any permanent changes to your plumbing. However, each model might need a slightly different approach. Thus, take these instructions as a general guideline and always make sure to consult the product manual carefully!
- Turn off the sink’s cold water supply.
- Open the kitchen faucet to flush out any remaining water.
- Disconnect the cold water line.
- Mount the filter system to the side of your kitchen cabinet.
- Connect the inlet hose of the under sink water filter system to the valve at the cold water line (not the hot water!) and tighten carefully.
- Connect the outlet hose of the filter system to the faucet inlet hose. Tighten carefully.
- Open the cold water line.
- Flush the system for a few minutes or as long as specified by the manufacturer.
Maintenance – When Should I Change the Filter Cartridge?
As with its installation, you don’t need to be a licensed plumber in order to maintain an under sink water filter properly. In most cases, all that’s required is timely and regular filter change (and maybe some cleaning).
Check the product manual to find out how often you have to replace the filters of your specific setup. Annual or biannual filter replacement are the norm. Although with well water, more frequent filter changes might be required especially with elevated sediment levels and water hardness.
That said, replacing under sink water filters should be a matter of minutes:
- Close the water supply valve feeding the system.
- Open the faucet to release water pressure from inside the filters.
- Remove the filter housings.
- Discard the old filter cartridges, clean each housing with mild soapy water, and insert the new cartridges.
- Screw the housings back with all O-rings properly seated.
- Turn the water supply back on and make sure to check for leaks.
Advantages & Disadvantages – Why You Should Install an Under Sink Water Filter
Advantages
- Installing an under-the-sink water filter system means a huge improvement in drinking water taste.
- The filtered water tastes better because it’s higher quality overall. Simply put, it contains up to 99% less contaminants. Depending on the specific setup, this includes potentially harmful heavy metals, all kinds of chemicals, inorganic compounds, etc.
- Speaking of setup, you can choose from many different products and opt for a system ideally suited for your needs.
- Under sink water filtration systems are designed to be compact.
- What’s more, most are super easy to install and maintain – think filter replacements.
- And when you move, the non-permanent installation allows you to take your filter system with you – great for renters.
- Last but not least, affordability. Under sink filters are budget-friendly.
Disadvantages
- An under counter water filter provides water for one outlet only.
- They’re quick to hook up, but unlike a pitcher, they aren’t installation-free. And if a system requires a separate faucet, you’ll have to drill a hole into your countertop or sink.
Under Sink vs. Countertop Water Filter Systems
Under sink and countertop water filters are both popular. Here’s a list of their similarities and differences.
Similarities & Differences
1. The Filtration Process
When compared to countertop water filters, under sink units are quite similar. They come as single-stage and as multi-stage units. You can also find reverse osmosis systems in both categories.
2. Filter Capacity
Again, not much of a difference. There are so many filter models on the market that you’ll find extremely low and extremely high filtration capacities in either group.
3. Size and Installation
Size and installation is where under sink or countertop filter does make a difference. First of all, while countertop water filters are highly compact for obvious reasons, under sink systems can be somewhat larger in size – not all of them, mind you.
Furthermore, countertop filters are mostly installation-free. They’re either autarchic or can be attached to any standard-sized kitchen faucet in under five minutes. Under sink filters on the other hand need to be properly installed.
4. Filter Replacements
Countertop and under sink filters are pretty similar when it comes to filter replacements.
Frequently Asked Questions (FAQ)
- Are undersink water filters worth it?
They are! Of course, not every undersink water filter is high quality, but a good filter system is designed to remove/reduce hundreds of contaminants from drinking water. - How do you hook up a water filter under the sink?
Compared to whole house setup, under sink water filter installation is not difficult at all. Inline units directly connect to your already existing sink faucet. Some filter systems, however, come with a separate faucet that might require you to do some drilling. - How do I choose an under sink water filter?
Most importantly, look for NSF certifications. They ensure that a certain water filter or water filter system removes all or at least the majority of harmful substances your water may contain. You should also pay attention to flow rate. Without a tank, water has to be filtered on demand. And you probably don’t want to wait two hours to fill one glass. Two more factors to consider are system size and maintenance (cost). - How do you clean an under sink water filter system?
It should be enough to clean your under sink water filtration system whenever you replace the filter elements. You can clean each filter housing with mild dish soap. Sanitize with bleach if need be. - How often should you change an under sink water filter?
How often to replace an under sink water filter depends on the capacity of the filter elements. Long-lasting ones are good for thousands of gallons of water, others for a couple hundred.
How We Chose and Tested the Best Under Sink Water Filters (Why Trust Us)
Here is a glimpse into our comprehensive methodology for reviewing under sink water filters:
- Establishing Criteria: Drawing from our extensive experience and research, we developed a list of 18 attributes to evaluate all products against.
- Initial Selection: We compiled an extensive list of both familiar and new under sink water filters available online, resulting in over 28 options.
- Thorough Evaluation: We meticulously examined product manuals, descriptions, warranties, and third-party certifications/test data based on standards established by the NSF, EPA, and CSA. Additionally, we conducted interviews with representatives from 5 reputable brands (Clearly Filtered, Aquasana, Epic, Waterdrop, Crystal Quest), posing questions as potential customers to assess their support level. This process narrowed down our list to 15 systems.
- User Feedback Analysis: To ensure only the highest-quality filters made the cut, we scoured various platforms for feedback and third-party ratings from real users. We carefully filtered out any fake or unreliable reviews.
- Hands-On Testing: We purchased and installed a selection of the systems onto a suitable water supply, allowing us to gain firsthand experience. Each under sink filter was meticulously evaluated from every possible angle, including size, ease of installation, maintenance, and filtered water pressure and taste. We ensured that each filter operated for a minimum of 3 weeks.
- Lab Testing: To further validate our findings, we conducted independent lab testing using reputable services like Tap Score. This allowed us to assess the real-life contaminant reduction rates of each filter.
- At this point, we had 9 products left. Finally, it was time to digest all this information, convert technical specs into insights that would be easy to grasp, and present everything in a pros vs cons manner.
Please note that all the information and ratings provided in this review are impartial and unbiased. Our content is also subject to professional fact-checking to ensure accuracy. Buddhini Dolapihilla, MBSS was instrumental in evaluating contamination reduction claims – think NSF certifications.
About Our Ratings
Our evaluation process for under sink water filters primarily focuses on the following key factors: Contaminant reduction rates based on NSF testing (30%), price and annual cost (25%), 1st hand testing and 3rd user opinions (20%), filter life (15%), customer service and product warranty (10%).
We’ve rated each system on a score of 1 to 5, with 5 being the highest rating.
Questions? Ask away!
About the Author Alexandra Uta
Information provided on BOS is for educational purposes only. The products and services we review may not be right for your individual circumstances.
We adhere to strict editorial guidelines. Rest assured, the opinions expressed have not been provided, reviewed, or otherwise endorsed by our partners – they are unbiased, independent, and the author’s alone. Our licensed experts fact-check all content for accuracy. It is accurate as of the date posted and to the best of our knowledge.