6 Best Tankless Under Sink Water Filters (*Update 2024)
Written by: Gene Fitzgerald // Expert Fact-Checking: Buddhini Dolapihilla, MBSS // Last Updated: Jan 31, 2024
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Top Pick: What’s the Best Tankless Under Sink Water Filter?
The best tankless under sink water filter in 2024 is the Clearly Filtered 3-Stage, because it has shown to be very powerful at filtering most types of water contaminants, it is easy to install & maintain, comes with a 30-day return policy and a limited lifetime warranty, and it has a long filter life (2,000 gallons).
Get ready to dive into the world of under sink water filters that make traditional tank systems feel as outdated as flip phones.
With a sea of options available, finding the perfect tankless under sink water filter for your needs can be like searching for a needle in a haystack. But fear not! We’ve rolled up our sleeves and put 21+ of the top models to the test – for the last several weeks, we’ve been on a mission to research, review, compare, and rank.
Also, our dedication to staying ahead of the game means this guide is continuously updated and improved, providing you with the most cutting-edge information. Time to upgrade your under sink game and say goodbye to clunky tanks. Let’s dive in!
Contents
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No Time to Read? Check Our List of the Best Tankless Under Sink Water Filters!
| Product | Details | |
|---|---|---|
 Best Overall: Clearly Filtered Tankless Under Sink Water Filter |
Overall Rating: 5.0/5.0 ⓘRatings based on filter methods, NSF, filter life, cost, direct testing, user ratings, product warranties, and other factors.
Get 10% Off! Use Code: |
Price: $$$ System Type: Inline Filter Life: 2,000 Gallons or 1 Year NSF Standards: 42, 53, 401 Annual Cost: $440 Read Review: Click Alexa’s Video Review: Click |
 Best for Reverse Osmosis: Waterdrop G3 |
Overall Rating: 4.0/5.0 ⓘRatings based on filter methods, NSF, filter life, cost, direct testing, user ratings, product warranties, and other factors.
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Price: $$$ System Type: Reverse Osmosis Filter Life: 550-2,200 Gallons NSF Standards: 58, 372 Annual Cost: ~$145 Read Review: Click Alexa’s Video Review: Click |
 Best Budget Pick: Epic Smart Shield |
Overall Rating: 4.5/5.0 ⓘRatings based on filter methods, NSF, filter life, cost, direct testing, user ratings, product warranties, and other factors.
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Price: $ System Type: Inline Filter Life: 651 Gallons NSF Standards: 42, 53, 401 Annual Cost: $115 Read Review: Click Alexa’s Video Review: Click |
 Best for Alkaline Water: Crystal Quest |
Overall Rating: 5.0/5.0 ⓘRatings based on filter methods, NSF, filter life, cost, direct testing, user ratings, product warranties, and other factors.
Get 5% Off! Use Code: |
Price: $$ System Type: Inline Alkaline Filter Life: 1-3 Years NSF Standards: – Annual Cost: ~$75-140 Read Review: Click |
 Best for Alkaline + RO: Frizzlife PD600-TAM3 |
Overall Rating: 4.0/5.0 ⓘRatings based on filter methods, NSF, filter life, cost, direct testing, user ratings, product warranties, and other factors.
|
Price: $$$ System Type: Alkaline RO Filter Life: 1-2 Years NSF Standards: – Annual Cost: ~$110 Read Review: Click |
Tankless Under Sink Water Filter Reviews
Our Top Picks
- Clearly Filtered – Best Overall
- Waterdrop G3 – Best for RO
- Epic Smart Shield – Best Budget Option
- Crystal Quest – Best for Alkaline Drinking Water
- Frizzlife PD600-TAM3 – Best for Alkaline + RO
- Aquasana Claryum 5300+ Max Flow
1. Best for Most Effective Contaminant Removal: Clearly Filtered 3-Stage Under the Sink Water Filter System
In our opinion, the best tankless under sink water filter in 2024 is the Clearly Filtered 3-Stage. That’s because it was third-party tested against NSF standards to remove the most contaminants among any under sink water filter we know.
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Clearly Filtered 3-Stage Under the Sink Water Filter System |
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| Price: | $$$ |
| Type: | Inline |
| Filter Capacity: | 2,000 gal |
| NSF: | 42, 53, 401 |
| Annually: | $440 |
|
Overall Rating: 5.0/5.0 ⓘRatings based on filter methods, NSF, filter life, cost, direct testing, user ratings, product warranties, 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: CF-UTSF
- Last Price: $550.00
- Filter Media/Process: Coconut Carbon Pre-Filter, Proprietary Blends
- Filter Stages: 3
- WxHxD: 15″x15.4″x3.1″
- Water Temperature: 38-85 °F
- Fitting: 3/8″
- Warranty: Lifetime (Limited)
Key Features & Pros
- Made in the USA.
- 3-stage tankless under sink filter system utilizes a blend of different media:
- Stage 1: Coconut shell granular activated carbon removes chlorine/chloramine, foul tastes and odors, as well as VOCs, and other common organic contaminants.
- Stage 2: Proprietary filter designed to remove heavy metals, pesticides, and herbicides, as well as difficult-to-remove contaminants like lead, chromium, and PFAS.
- Stage 3: The final filter stage is another proprietary blend designed to remove fluoride and arsenic without the need for reverse osmosis and its resulting wastewater.
- The system is tested against NSF standards 42, 53, and 401.
- Features some of the most thorough testing we’ve seen. More than 200 contaminants tested successfully.
- Does not remove healthy essential minerals from your water.
- The inline design makes installation a breeze as it connects directly with your sink’s cold water supply line.
- Installation is simple and can be done in less than 15 minutes.
- Non-permanent installation makes the system a great option for renters.
- Can be installed horizontally, vertically, or leaned against the wall.
- Stainless steel inlet and outlet hoses for leak-free use.
- Maintenance is minimal.
- 2,000-gallon capacity equates to approximately once-a-year filter changes.
- No tool filter changes. Simply twist on and twist off.
- Subscribing to auto-ship saves you 10% on replacement filters.
- 30-day money-back satisfaction guarantee in case anything goes wrong.
- Limited lifetime warranty on the system.
Cons
- Replacement filters are on the expensive side even with the 10% auto-ship discount.
- Water pressure reduction of 25% to 35% is typical.
- While the system offers excellent quality, thorough testing, and is made in the USA, it costs significantly more than many other tankless under sink water filters.
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
If you’re looking for the most effective tankless under sink water filtration system, then the Clearly Filtered 3-Stage is your best option.
→ Get the Full Clearly Filtered Under Sink Review
2. Best for Reverse Osmosis: Waterdrop G3 Tankless System
Want a tankless under sink water filter that applies reverse osmosis? We recommend the Waterdrop G3!
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Waterdrop G3 Tankless Under Sink Reverse Osmosis System |
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| Price: | $$$ |
| Type: | RO |
| Filter Capacity: | 550-2,200 gal |
| NSF: | 58, 372 |
| Annually: | ~$145 |
|
Overall Rating: 4.0/5.0 ⓘRatings based on filter methods, NSF, filter life, cost, direct testing, user ratings, product warranties, and other factors.
Get 10% Off! Use Code: |
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Alexa’s Video Review
Being part of the BOS team, Alexa 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! Alexa 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/Process: Sediment, 2x Carbon Block, RO Membrane
- Filter Stages: 4
- Flow Rate: 0.42 gpm
- Recovery Rate: 66%
- WxHxD: 5.67″x17.72″x18.12″
- Water Temperature: 41-100 °F
- Water Pressure: 14.5-87 psi
- Warranty: 1 Year
Key Features & Pros
- The tankless reverse osmosis system offers the same filtration effectiveness as a typical RO system but in a compact tankless design.
- The system features four distinct filter stages:
- First, a composite blend of activated carbon and sediment filter separates and removes sediment and chlorine – both contaminants that can damage the RO membrane.
- Next, the ultra-fine RO membrane uses reverse osmosis to separate and flush out total dissolved solids (TDS) like chromium and other heavy metals, fluoride, PFAS, microbial contaminants, and so much more.
- Finally, an activated carbon post-filter gives the water a final ‘polish’, removing any leftover taste/odor and organics.
- The system features NSF/ANSI 58 and 372 certification for TDS removal and lead-free material.
- The built-in pressure pump increases the flow rate to approximately 0.4 gallons per minute.
- The pump also reduces wastewater generation to about 2 cups pure to 1 cup wastewater.
- Will pour a normal glass of water in approximately 8 seconds.
- LED display screen on the faucet allows you to monitor TDS levels and check the remaining filter life at a glance.
- A white LED indicates healthy filters, a yellow LED indicates less than 40 gallons of filter usage are left, and a red LED plus a beeping noise indicates it is time to change filters.
- The unit’s front panel also displays the TDS information.
- BPA-free and lead-free materials.
- Installation is no more difficult than with other reverse osmosis systems (actually, it’s easier!), and can typically be completed in less than an hour or two
- Tool-fee filter changes take just 10 seconds. Simply twist, remove, and replace. Does not require shutting off feed water.
- The annual cost for filter replacement is just $145.
- The manufacturer offers a 30-day money-back satisfaction guarantee if you’re unhappy for any reason.
- 1-year manufacturer warranty on the system.
Cons
- We’d like to see additional specific contaminant reduction rates.
- Like other RO systems, the system is prone to ‘TDS creep’. This means when the system hasn’t been used for a while it requires flushing a gallon or so of water until the TDS reading falls into the optimal range.
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 the best tankless under sink filter utilizing reverse osmosis filtration.
→ Get the Full Waterdrop G3 RO Review
3. Best for Lower Budgets: Epic Smart Shield Under Sink Water Filter
The Clearly Filtered tankless under sink water filter is out of your budget? In this case, the Epic Smart Shield might be ideal for you – it’s much more affordable!
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Epic Smart Shield Tankless Under Sink Water Filter |
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| Price: | $ |
| Type: | Inline |
| Filter Capacity: | 651 gal |
| NSF: | NSF 42, 53, 401 |
| Annually: | $115 |
|
Overall Rating: 4.5/5.0 ⓘRatings based on filter methods, NSF, filter life, cost, direct testing, user ratings, product warranties, and other factors.
Get 20% Off! Use Code: |
|
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
- Filter Media/Process: Carbon Block
- Flow Rate: 1.25 gpm
- WxHxD: 4.25″x19.75″x4.5″
- Water Temperature: 33-100 °F
- Water Pressure: 40-120 psi
- Fitting: 3/8″ NPT
- Warranty: Lifetime
Key Features & Pros
- Affordable!
- The entire system is made in the USA.
- Can be used on both well water and municipal water supplies.
- Well water users and anyone with high levels of sediment should consider installing an additional 5-micron Epic Smart Shield sediment pre-filter to protect the system from premature clogging.
- Tankless activated carbon filter removes up to 99.99% of 70 known contaminants including: Particulates, chlorine taste and odor (5%), chloramine (95.5%), lead (>99.3%), cysts (>99.9%), asbestos (>99%), VOCs (99.6%), mercury (96.6%), turbidity, BPA, MTBE, Ibuprofen, Estrone, Naproxen, Phenytoin, PFOA + PFOS, microplastics, and many more.
- NSF certified against standard 42, 53, and 401.
- Installation is simple and easy – can be completed in just 20 minutes or less even if you don’t have previous plumbing experience.
- Quick connect fittings and inline design make installation a breeze.
- An installation kit with included feed water adapter and connection hoses comes included.
- The inline design means the system directly connects to your existing faucet and cold water supply. No cutting into plumbing lines is required. But: Optional kit with polished chrome faucet available.
- Maintenance is also a breeze. All that’s required is changing the cartridge when required.
- The manufacturer recommends every 14 to 16 months for light use (single person), 12 months for normal use (couple), or 9 to 12 months for heavy use (larger family or heavy use with cooking/plants/pets).
- The annual cost is approximately $115 or 20% less if you subscribe to Epic’s Clean Water Club.
- The company also offers a filter recycling program where you can send back three used filters and receive a free filter in exchange.
- Epic offers excellent customer service and support, as well as a lifetime warranty and return policy.
Cons
- With a flow rate of 1.25 gpm, the system may lead to some pressure drop at your faucet.
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 the best choice for people on a budget.
→ Epic Smart Shield Fully Reviewed
4. Best for Alkaline Drinking Water: Crystal Quest Tankless Under Sink Filter
Are you into alkaline drinking water? Check out this system by Crystal Quest!
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Crystal Quest Tankless Under Sink Alkaline Filter System |
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| Price: | $$ |
| Type: | Inline Alkaline |
| Filter Capacity: | 1-3 Years |
| NSF: | – |
| Annually: | ~$75-140 |
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Overall Rating: 5.0/5.0 ⓘRatings based on filter methods, NSF, filter life, cost, direct testing, user ratings, product warranties, and other factors.
Get 5% Off! Use Code: |
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Other Specs
- Model: CQE-US-00340
- Last Price: $256.80
- Filter Media/Process: 5-Micron Carbon Block, GAC + Catalytic Carbon + KDF + Ion Exchange + Mineral Balls, Mineralization Filter
- Filter Stages: 3
- Flow Rate: 0.3-0.5 gpm
- WxHxD: 15″x14″x5″
- Water Temperature: 40-90 °F
- Water Pressure: 20-60 psi
- Fitting: 1/4″
- Warranty: 1 Year
Key Features & Pros
- Tankless filter system features three distinct filter stages:
- A 5-micron carbon block filter traps sand, silt, dirt, and other particles which could damage the later filter stages. It also removes pesticides, herbicides, volatile organic compounds (VOCs), chlorine, and other chemicals like disinfection byproducts.
- The second sage is Crystal’s proprietary filter stage comprised of both catalytic coconut shell and granular activated carbon, ERA-6500 and ERA-9500 KDF media, and an anion exchange resin. Combined, this blend of media will remove or reduce heavy metals, chlorine/chloramine, pesticides and herbicides, pharmaceuticals, inorganic contaminants, and more. This stage also features ceramic and tourmaline balls – which help to maintain an alkaline pH and enhance the water’s taste.
- Finally, an alkalizing cartridge with both magnesium and calcium carbonate increases pH levels and boosts oxygenation.
- Installation is no more complex than with other tankless under-the-sink systems.
- You can opt for either copper tubing or flex tubing depending on your existing plumbing lines.
- Installation hardware and faucet both come included.
- Maintenance requirements are also low.
- All that’s required is changing the alkaline and carbon block filter cartridges periodically. Both have between 12 and 18-month lifespans, depending on usage and water quality.
- SMART filter cartridge will last for up to 3 years before needing replacement.
- Annual maintenance costs total just $75 to $140.
Cons
- Doesn’t feature any NSF testing or certifications.
- Installing the system without the use of a licensed plumber voids the one-year manufacturer warranty.
- The flow rate of 0.3-0.5 gallons per minute is definitely on the lower end.
Our Rating
- Filtration Performance: 4.5/5.0
- Filter Life: 5.0/5.0
- Price: 5.0/5.0
- Maintenance Cost: 5.0/5.0
- Overall: 5.0/5.0
Best for
This Crystal Quest tankless under sink filter is the best option if you’re looking for thorough filtration plus alkaline drinking water.
5. Best for Alkaline Water + RO: Frizzlife PD600-TAM3
We recommend the PD600-TAM3 by Frizzlife if you want both reverse osmosis water purification as well as alkaline drinking water – all in a tankless design.
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Frizzlife PD600-TAM3 Tankless Reverse Osmosis Water System |
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| Price: | $$$ |
| Type: | Alkaline RO |
| Filter Capacity: | 12-24 Months |
| NSF: | – |
| Annually: | ~$110 |
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Overall Rating: 4.0/5.0 ⓘRatings based on filter methods, NSF, filter life, cost, direct testing, user ratings, product warranties, and other factors.
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Other Specs
- Model: PD600-TAM3
- Last Price: $469.99
- Filter Media/Process: Sediment + Carbon Filter, RO, Carbon + Remineralization
- Filter Stages: 8
- Flow Rate: 0.41 gpm
- Membrane Rating: 600 gpd
- Recovery Rate: 60%
- WxHxD: 5.3″x15.5″x14.7″
- Weight: 33.06 lb.
- Water Temperature: 39-100 °F
- Water Pressure: 20-80 psi
- Fitting: 3/8-1/2″
- Warranty: 1-1.5 Years
Key Features & Pros
- Tankless under sink system features three distinct filter cartridges:
- First, a 2-in-1 composite filter with both activated carbon and pleated polypropylene removes foul odor and taste, chlorine/chloramine, and other organic pollutants as well as floating particles.
- Next, the reverse osmosis membrane removes a wide range of contaminants including lead, radium, cadmium, chromium, TDS, cysts, fluoride, arsenic, PFOA and PFOAS, and more.
- Lastly, a remineralization and alkalinization filter stage restores the water’s pH to a weak alkaline level of at least 7.5 pH. It also adds back essential minerals removed by the reverse osmosis stage. More activated carbon is used to capture any remaining impurities.
- The water flow rate of 0.41 gallons per minute is possible due to the internal pump. While not particularly high when compared with other tankless water filter systems, this is quite impressive for a system utilizing reverse osmosis.
- Will fill a normal-sized glass in just 10 seconds.
- The internal pump also significantly reduces wastewater generation. System produces just 1 gallon of wastewater for each 1.5 gallon of filtered water.
- The space-saving tankless design allows for installation in tight spaces.
- Smart display panel offers a real-time reading of TDS levels and filter life remaining.
- Simple way to know when it’s time to change filters.
- Eye-catching stainless steel faucet included.
- Installation is simple and can be accomplished in a few hours or less.
- Step-by-step installation instructions and video are included.
- Maintenance is also very straightforward.
- Simply twist to remove and replace the filter cartridge.
- Stages 1 and 3 last for approximately 12 months each, while the membrane will last about 2 years.
- Maintenance costs total just $110 per year.
Cons
- Quite pricey.
- No NSF testing or certification is available for precise contaminant removal figures.
- Some users reported issues with leaks, the filter indicator malfunctioning, and slow flow. Support wasn’t always helpful.
Our Rating
- Filtration Performance: 4.0/5.0
- Filter Life: 5.0/5.0
- Price: 4.0/5.0
- Maintenance Cost: 5.0/5.0
- Overall: 4.0/5.0
Best for
The Frizzlife PD600-TAM3 is the best option for a combination reverse osmosis and alkalinization filter system.
→ Read the Full Frizzlife PD600-TAM3 RO System Review
6. Aquasana Claryum Max Flow Tankless Under Sink Water Filter
Finally, let’s review the Aquasana Claryum Max Flow Tankless Under Sink Water Filter!
Aquasana Claryum 5300+ Max Flow Tankless Under Sink Water Filter |
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| Price: | $$ |
| Type: | Inline |
| Filter Capacity: | 800 gal |
| NSF: | NSF 42, 53, 401, P473 |
| Annually: | ~$160 |
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Overall Rating: 4.0/5.0 ⓘRatings based on filter methods, NSF, filter life, cost, direct testing, user ratings, product warranties, and other factors.
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|
Gallery
Other Specs
- Model: AQ-5300+
- Last Price: $224.99
- Filter Media/Process: 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
- Water Pressure: 20-80 psi
- Fitting: 3/8″
- Warranty: 1 Year
Key Features & Pros
- Tankless under sink filter system can remove up to 99% of 78 common contaminants.
- 3-stage design:
- Stage 1: 20-micron sediment pre-filter removes dirt, dust, rust, silt, and other sediment that can clog the later stages.
- Stage 2: Activated carbon primarily removes chlorine, bad tastes and odors, and few organics.
- Stage 3: A Claryum filter block (catalytic carbon + ion exchange resin) removes chlorine/chloramine, cysts, mercury, lead, PFOA/PFOS, asbestos, pesticides, etc.
- Selective filtration retains essential minerals including potassium, calcium, and magnesium.
- Tested and certified to NSF/ANSI standards 53, 42, 401, as well as protocol P473.
- The system faucet is offered in three different premium metal finishes: brushed nickel, oil-rubbed bronze, and chrome.
- Installation is simple and straightforward.
- All components for installation are included.
- Detailed installation instructions and videos are included.
- Maintenance requirements are relatively low.
- All that’s needed is changing the filter cartridges periodically.
- Filter capacity is 800 gallons or 6 months – whichever comes first.
- Filter cartridges can be changed without shutting off the water supply.
- Build in sound alarm and red LED to indicate when the filter needs changing.
- 1-year manufacturer warranty included.
- Aquasana’s customer service is responsive and knowledgeable.
Cons
- A small portion of users have related issues with faulty O-rings, tubing coming loose, damaged filter housings, and defective faucets leading to leakage.
- Another small cohort of users complained of low-pressure issues.
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
The Aquasana Claryum Max Flow Tankless Under Sink Water Filter is best used for thorough broad-based water filtration without reverse osmosis.
→ Get the Full Aquasana 5300 Max Flow Review
More Reviews:
- Best Under Sink Water Filters
- Best Under Sink Water Filter for Well Water
- Best Single-Stage Under Sink Water Filters
- Which Is the Best Under-the-Sink Hot & Cold Water Filter System?
- Best Alkaline Under Sink Water Filter
- This Guide Will Help You Find the Best Under Sink Carbon Filter System!
- Inline Under Sink Water Filter Reviews
- List with All Under Sink Water Filters Featured on BOS
Comparison List
(Mobile Hint: Swipe to Scroll)
| Model | Price | Type | Filter Process | Stages | Filter Capacity | NSF | Annually | Warranty | Additional Info |
|---|---|---|---|---|---|---|---|---|---|
| Clearly Filtered 3-Stage Under the Sink Water Filter System | $$$ | Inline | Activated Carbon, Proprietary Blends | 3 | 2,000 gal | 42, 53, 401 | $440 | Limited Lifetime | |
| Waterdrop G3 Tankless Under Sink Reverse Osmosis System | $$$ | RO | Sediment, Carbon Blocks, RO | 4 | 550-2,200 gal | 58, 372 | ~$145 | 1 Year | |
| Epic Smart Shield Tankless Under Sink Water Filter | $ | Inline | Carbon Block | 1 | 651 gal | 42, 53, 401 | $115 | Lifetime | |
| Crystal Quest Tankless Under Sink Alkaline Filter System | $$ | Inline Alkaline | Carbon Block, GA, Catalytic Carbon, KDF, Ion Exchange, Mineral Balls, Mineralization | 3 | 1-3 Years | – | ~$75-140 | 1 Year | |
| Frizzlife PD600-TAM3 Tankless Reverse Osmosis Water System | $$$ | Alkaline RO | Sediment + Carbon Filter, RO, Carbon + Remineralization | 8 | 12-24 Months | – | ~$110 | 1-1.5 Years | |
| Aquasana Claryum 5300+ Max Flow Tankless Under Sink Water Filter | $$ | Inline | Sediment Pre, Activated Carbon, Catalytic Carbon, Ion Exchange, Submicron Filtration | 3 | 800 gal | 42, 53, 401, P473 | ~$160 | 1 Year |
Buying Guide: How to Choose the Tankless Under Sink Water Filter That’s Best for You
The following are key features worth considering when shopping for a tankless under sink water filter. They will help you choose the right on for your needs and budget.
Water Flow Rate and Pressure
Tankless water filter systems differ from tanked water filters in that they process water on demand rather than keeping a reserve of water on hand for use. As a result, the flow rate is of particular importance, as you’ll need to wait for the system to filter fresh water every time you open the faucet.
So, you’ll want to consider your water usage requirements carefully when picking out a tankless system, as too low of a flow rate means you’ll need to wait every time you pour a glass of water. This can be particularly problematic if you have a larger family with significant water demands.
Typically, tankless under sink systems without a reverse osmosis stage have a high enough flow rate that you won’t notice the slow flow speed that much. Reverse osmosis systems tend to have lower flow rates, which can present an issue depending on your water usage.
Your Water Quality
Anytime you’re investing in a water filter system, the first step is getting your water tested. This will give you information on contaminants in your water so you can tailor your filter purchase to eliminate them.
The best method to determine your water quality is through testing. For well water, this can either be done with a home test kit or by sending in a sample for professional testing. Home test kits are cheaper and offer instant results but are less accurate than professional testing – which will give you accurate data both on contaminants and their precise contaminants.
For municipal water, if you don’t want to do your own testing there are publicly available resources like the EWG Tap Water Database.
The Filter Process (Filtration Stages)
The filtration process refers to the specific filter stages that your water passes through.
As far as tankless under sink water filters are concerned, there is a wide range of possible filter stages, including sediment, activated carbon, KDF, ion exchange, reverse osmosis, remineralization, and more.
Generally speaking, the more filter stages a system has, the higher the quality its treated water will be. The only issue with this is that more filter stages also mean increased maintenance demands and costs.
NSF Standards
NSF standards refer to the third-party organization that conducts independent testing and issues certifications for water filter systems. NSF certifications are the best way to ensure that your system will actually remove the contaminants claimed by the manufacturer.
While there are many NSF standards pertaining to removing different contaminants some of the more common ones to be aware of are NSF Standard 42 (chlorine/chloramine, taste and odor, and particulate removal), NSF Standard 58 (contaminants removed by reverse osmosis), NSF 53 for plenty of contaminants with health effects, and NSF Standard 401 (emerging compounds).
Installation
Tankless under sink filters are typically not difficult to install, and most can be put up and running in less than an hour with basic tools. This is particularly true for systems with an ‘inline’ design, which simply hook into your existing under sink water supply and don’t require any cutting or drilling.
Systems with dedicated faucets may require drilling into your countertop or sink, although this is not always the case, as some can be mounted in an existing soap dispenser/water jet hole. This can be a little tricky if you’ve never done it before, but is not as hard as it looks.
Another point to note is that reverse osmosis systems will require a drain hookup in order to drain away the contaminant-filled wastewater. This typically involves drilling a hole into the drain pipe under your sink to install a drain saddle.
Filter Life and Maintenance
Tankless or not, under sink water filters are typically simple to maintain. The only major maintenance task here is changing the filter cartridges when they exceed their capacity.
Keep in mind that the manufacturer stated filter capacity is based on ideal conditions and real-life values will vary based on your usage and level of contaminants in your water.
Many of the above systems feature a twist on/off design, which allows for near-instant filter changes without the need to shut off the water supply.
Space
While tankless systems take up significantly less space than their tanked counterparts, they nonetheless require some real estate under your sink to install. If you have limited space in your under sink cabinet, be sure to look up the unit dimensions before purchasing.
Cost
Tankless under sink filters vary widely in terms of cost, with some available for just over $100, while others cost well over $500.
One more important factor to keep in mind when considering a filter system is its annual filter replacement cost.
It’s important to consider the annual filter replacement cost and not the per-unit cost, as filters have differing lifespans, and a low-cost filter with a short lifespan can have a higher annual cost than a higher-priced filter with a longer lifespan.
Product Warranty
Any time you’re considering shelling out significant money on a filter system, a solid warranty is important for peace of mind. Some of the above systems feature lifetime warranties, and some also feature money-back satisfaction guarantees in case you aren’t satisfied with the system’s performance for any reason.
More on Tankless Under Sink Water Filters
Further Reading:
What Is a Tankless Under Sink Water Filter?
A tankless under sink water filter system is any system designed to be installed under your sink without a storage tank. The lack of a storage tank makes these systems space-saving and easier to install + maintain, as there’s no need to set up or clean/sanitize the tank.
As no storage tank is used, the flow rate becomes extremely important for these water filters. Unlike tanked systems, which keep a reserve of filtered water on hand at all times, tankless systems must filter fresh water every time you open the faucet, so a low flow rate can have a significant impact on the system’s functionality.
The Different Types of Under Sink Water Filters and How They Work
Let’s take a look at some of the different types of tankless under sink water filter systems and how they operate.
Dedicated Faucet vs Inline Design
An important consideration when choosing an under sink system is whether it features an inline design or a dedicated faucet.
An inline design means the system is installed in line with your existing water supply line and faucet, and no additional plumbing is required. As inline systems utilize your existing faucet, every time you open the cold water on your faucet, fresh filtered water is dispensed. These systems are exceptionally easy to install, as no drilling or cutting through plumbing lines is typically required.
Systems with dedicated faucets, on the other hand, require installing a separate water faucet on the sink or countertop, which may require drilling through the sink or countertop material. They also connect to the cold water supply under the sink, but use a separate line to send filtered water to the dedicated faucet. These systems are somewhat more difficult to install but offer the advantage of having separate faucets for filtered and non-filtered water.
Single vs Multi-Stage Systems
Single stage systems offer basic single-stage water filtration, while multi-stage systems offer multiple filtration stages for a more thorough filtration process.
Multi-stage systems often combine sediment pre-filtration with activated carbon and/or specialized filter stages like KDF media or ion exchange. Sediment pre-filtration is used to remove dirt, sand, silt, and other particulates that can clog the later filter stages, while activated carbon removes chlorine, pesticides, VOCs, and foul odors and tastes.
Reverse Osmosis
Some tankless under sink systems use reverse osmosis as part of the water filtration process. Reverse osmosis is a highly effective filtration process that uses an ultra-fine membrane to separate out contaminant particles down to just .0001 microns in size.
RO works slightly differently than other filters in that it doesn’t actually trap the contaminants but rather separates them and then flushes them away. As a result, these systems require a drain hookup to flush away the contaminant-filled wastewater.
Additionally, RO systems tend to have a significantly lower flow rate than other tankless systems. The trade-off between enhanced filtration and a lower flow rate is something you’ll want to consider when buying.
Advantages of Tankless Under Sink Filter Systems
Space Saving
One of the primary advantages of using a tankless under sink water filter is the space you’ll save. A typical 3.2-gallon storage tank measures approximately 12” x 14”, and when combined with the rest of the system takes up a significant portion of the real estate under your sink.
A tankless system removes the need for a storage tank and can be installed in significantly smaller spaces and cabinets.
No Stagnant Water for Improved Taste
While storage tanks have their purpose, they can also have issues with imparting a stagnant taste to your filtered water. This tends to occur in reverse osmosis systems when the rubber bladder inside the tank leaches a poor taste into the water.
Tankless systems don’t have this issue, and won’t impart any unpleasant taste into your water.
Easy to Install & Maintain
Storage tanks require regular cleaning/sanitizing as well as occasional repressurizing in order to keep them functioning properly. Additionally, they can encounter other issues like the internal rubber bladder rupturing, or losing pressure over time.
Tankless systems, as you might expect, don’t have any of these issues and are easier to install and maintain as a result.
Smart Features
Tankless systems – especially reverse osmosis systems – often come with special features like digital filter life indicators, TDS reading indicators, and more. These are nice to have, although not necessary by any means.
Disadvantages of Tankless Systems
No Water Storage in Emergencies
While tankless under sink water filters offer several advantages over tanked systems, as no storage tank is used, there is no reserve of water on hand in case of emergencies. This is not a major disadvantage but something to be aware of nonetheless.
Flow Rates
As mentioned previously, flow rates can be a cause for concern with tankless systems, especially ones with a reverse osmosis stage. This is of particular importance when it comes to larger families with higher water consumption.
Tankless RO Systems Are More Expensive
Lastly, tankless systems, especially ones with RO stages, are more expensive than tanked systems for the most part.
Tank-Based vs Tankless Under Sink Water Filters
When it comes to tank-based vs. tankless under sink water filters, there isn’t a clear winner per se, instead, it comes down to personal preference.
On the one hand, tankless systems are smaller and can be installed in spaces too tight for tanked systems, they’re easier to install and maintain, won’t impart a stagnant taste to your water, and some offer advanced features.
Tanked systems, on the other hand, offer the flexibility of storing a reserve of water, are less expensive, and are less prone to issues with low flow rates.
Frequently Asked Questions (FAQ)
- Are tankless under sink water filters worth it?
Yes, they are! You just need to make sure that the filtration process is powerful and suits your water conditions. - Which is better, tankless or tank-based under sink filters?
There is no general answer. Both can be good and it depends on your individual situation and preferences. Tankless saves space, while tank-based always has water ready. - What is the best tankless under-the-sink water filter for heavy metals?
We would probably go with the Clearly Filtered or the Waterdrop G3.
How We Chose and Tested the Best Under Sink Water Filters (Why Trust Us)
As a seasoned water treatment expert, we take great pride in presenting you with our methodology for reviewing tankless under sink water filters:
- Step 1: Establishing Criteria – Drawing from our years of experience, we developed a list of 18 vital attributes to measure all the products against.
- Step 2: The Quest Begins – We embarked on a grand quest to compile an extensive list of both familiar and new tankless under sink water filters available online. Our search yielded a staggering number of 21+ units, ready to undergo our rigorous examination.
- Step 3: The Thorough Evaluation – We delved into the depths of product manuals, descriptions, and third-party certifications/lab reports. As potential customers, we also dug deep to assess the level of support and dedication some of the filter brands had to offer. This intensive process whittled down our list to only the top 11 systems worthy of your attention.
- Step 4: Unmasking the Truth – To ensure only the best tankless under sink filters made the cut, we relied on real user feedback from Amazon, Walmart, Best Buy, and other sites. With an eagle eye for authenticity, we filtered out any fake or unreliable reviews.
- Step 5: Hands-On Testing – With a sense of excitement and anticipation, we procured and installed a selection of the 5 remaining systems onto our water supply. With each installation (following instructions to the T), we gained firsthand experience, subjecting each filter to a rigorous evaluation from every possible angle. Ease of installation, priming, flow rates, filter replacement, and the most important factor of all – water taste – were assessed (among other things). We spared no effort, ensuring that each filter performed flawlessly for a minimum of 3 weeks.
- Step 6: Unleashing the Power of Science – To further bolster our findings, we called upon the expertise of independent laboratories. With reputable services like Tap Score at our side, we conducted extensive lab testing. This allowed us to unveil the true potential of each tankless under sink water filter, assessing their real-life contaminant reduction rates. The numbers don’t lie, and we bring them to you with absolute transparency.
- Step 7: The Final Showdown – After an arduous journey, only 5 products remained. It was time to put together our buying guide, allowing you to make an informed purchase decision with clarity and confidence.
- Step 8: The Pledge of Impartiality – Rest assured, our information and ratings are impartial and unbiased. We have subjected our content to professional fact-checking, ensuring accuracy and integrity in every word. For example: Buddhini Dolapihilla, MBSS played a critical role in evaluating claims of contamination reduction, which involved online verification of NSF/ANSI certifications and lab data.
About Our Ratings
Our evaluation process for tankless under sink water filters focuses on the following factors: NSF-backed contaminant reduction rates (30%), costs (25%), hands-on testing and user opinion (20%), filter capacity (15%), product warranty/support (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 Gene Fitzgerald
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.