Best under sink water filter: 6 filters compared

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BEST OVERALL
Sale 13%
iSpring CU-A4 Under Sink Water Filter System

The iSpring CU-A4 is our pick for the best overall water filter system. It’s the most thorough in removing multiple contaminants. It has an ultrafiltration membrane that removes contaminants down to 0.1 microns which is the same level as some reverse osmosis systems - it can clear out almost 99% of all the contaminants in the water. The other advantages are that it has a relatively long lifespan and its water pressure stays strong.

BEST VALUE
Sale 22%
Frizzlife MK99 Under Sink Water Filter

The Frizzlife MK99 is the most affordable option on the list but it does an efficient job too at removing common contaminants from the water. Besides that, the water flow is fast and it has a relatively longer lifespan than other similar under sink water filters in the same price range. The overall quality of the unit is also quite incredible for such an affordable price.

Under sink water filters are less complex and bulky compared to reverse osmosis systems or whole-house filtration systems. They are also able to efficiently get rid of more contaminants than water filter pitchers or countertop water filters. They are very convenient for those that don’t want the maintenance, cost, and bulkiness that comes with RO or whole-house systems.

This review looks at 6 of the top under sink water filters on the market and we will highlight their filtration performance, expected lifespan, flow rate, and their overall standpoint based on the feedback from users.

1. iSpring CU-A4

Best under sink water filter
Sale 13%
iSpring CU-A4 4-Stage 0.01 micron High Capacity Premium Under Sink Drinking Water System, Tankless,...
  • SUPERIOR PERFORMANCE: The advance 4-stage design, which includes both Ultrafiltration and KDF/GAC stages removes up to 99% of most problematic pollutants such as chlorine and chlorine treatment by-products, lead, arsenic, and much more, while retaining healthy minerals. Noted: This system does not affect TDS as Reverse Osmosis System does
  • 4-Stage ULTRA FILTRATION SYSTEM: PP Sediment Filter ((5 microns) removes larger particles like rust, sand, dirt. ) Ultra Filtration Filter (contains hollow fiber membrane technology with a pore size of just 0.01 microns. ) KDF and GAC Filter (provides much better control of particularly problematic contaminants including chloramine, hydrogen sulfide, heavy metals, and other compounds). Fine Activated Carbon Filter (provides final polishing before the purified water).
  • SIMPLE AND FLEXIBLE: NO WASTE WATER and No storage water tank required. The CU-A4 provides highly effective water filtration for any number of clean-water needs - at the sink, in the refrigerator, for coffee makers and more.

Specifications

  • Dimensions: 10.63 x 4.33 x 12.6 inches 
  • Weight: 2 kilograms
  • Filtration capacity: 1100 gallons
  • Flow rate: 0.5 to 0.9 GPM
  • Filtration method: PP sediment filter (5 microns), ultrafiltration membrane (0.1 microns), KDF and activated carbon compound filter, and post activated carbon filter.
  • Warranty:  1 year
  • Features: dedicated faucet, reversible feed water adapter (fits ½” or  ⅜” water valve)

Things to Like

  • Performs extensive filtration – the four filters do a thorough filtration work removing up to 99% of bacteria, cysts, giardia, cryptosporidium, VOCs, and chlorine. They also eliminate 98% of heavy metals (lead, mercury, copper, and nickel). Iron (95%), asbestos, pesticides, germicides, pharmaceuticals, PFOS, PFOA, particulates are all as well removed. The result is very clean filtered water that has no bad smell and tastes great.
  • The filters have a relatively long lifespan – the ultrafilter membrane lasts about 12 months before requiring replacement while the other three filters have 1100 filtration capacity which lasts about 6 months before replacement. All the filters work effectively throughout their lifespan. They don’t fail midway hence you get full service out of them. 
  • The water pressure stays strong – the flow rate is around 0.5 to 0.9 GPM depending on the pressure of the source water. It’s not the fastest, but it’s not slow either considering it has four filters. You can fill a 1-gallon (128 ounces) bottle in about one minute or less.
  • Simple installation and maintenance – installing the set is quick and takes little effort. The tubings are color-coded while the fittings are of the push-to-connect type. They snap on with ease. Installing the faucet is the only thing that may require some plumbing skills although you can avoid it by installing the set as an inline water filter. Changing the filters is straightforward. It’s a simple twist on/off process.
  • Well built using durable plastic material – the entire unit including the filter cartridges is sturdy and made using a solid plastic material. The fittings are equally sturdy and connect tightly such that they don’t leak. The provided faucet is all-metal construction too, hence it can last long. 

What not to like?

  • Larger in size – the iSpring CU-A4 is slightly large due to its four filter cartridges which take up more room than other under sink water filters.
  • A bit of plastic taste and oily sheen in the beginning – some users reported that the filtered water initially has an oily sheen on top (from the oil used to seal the cartridges) while others mentioned that it tends to taste a bit like plastic. You have to flush the unit with several gallons of water first after installation to get rid of the plastic taste and the oily sheen. 
  • Installation instructions are not clear – the provided installation manual is not straightforward. The directions don’t adequately explain how to carry out the water connections, so installation may take longer or be slightly challenging for those that haven’t installed any under sink water filters before.
  • Replacement filters are hard to find – there were few complaints that the replacement filters for this iSpring model are difficult to find. They are not available on the manufacturer’s website or Amazon. There’s no timer or filter life indicator either to alert you when the filter needs to be changed. 
  • Maintenance costs can be higher – the iSpring CU-A4 requires the most filter changes on our list because it uses 4 filters while the rest have two or are just a single filter cartridge. Therefore, with the two carbon filters and the sediment filter requiring replacement every 6 months, the maintenance cost will likely be higher than the rest. 

Final Remarks  

If you want a robust under sink water filter that can efficiently remove just as many contaminants as an RO system without water wastage, then the iSpring CU-A4 is an ideal choice. It’s an option you can consider too for filtering less contaminated well water. The major contaminants it can’t remove are viruses, chloramine, and fluoride. 

2. Frizzlife MK99

Best value under sink water filter
Sale 22%
Frizzlife Under Sink Water Filter System-NSF/ANSI 53&42 Certified High Capacity Direct Connect Under...
  • ✔Two-stage Advanced Water Purifier With 0.5 Micron: The Frizzlife MK99 Water Filtration System includes a TWO-STAGE High precise compound filter, which has a unique technology that removes over 99.99% of contaminants while leaving in all essential minerals. Reduces Lead, Heavy Metals, Chlorine, Chromium 6, Mercury, Rust, Volatile Organic Compounds, Carcinogens, and other contaminants, such as Turbidity, Odors and Bad Tastes. Enjoy pure and healthy water from the tap. No more bottled water!
  • ✔Fits both 1/2" and 3/8" cold water line: Super Easy Installation. Come with 3/8" Directly Connect hoses that fit standard 3/8" feed water valves under US kitchen sinks. The Inline water filter system also comes with a 3/8" to 1/2" converter fittings that allow the system to directly install to the existing both 1/2" and 3/8" cold water line and faucet under your sink. Took less than 3 minutes and No Plumbing Required! New installation video available.
  • ✔Best Auto Shut Off Design: Utilizing quick change twist-in installation design makes it take less than 3 minutes for you to install the system or doing a filter replacement. Provides quick twist connection for easy, tool-free, no mess filter replacement. The filter cap is designed with a BUILT-IN shut off valve. You don't even need to shut off the water supply whenever you work on the filter cartridge replacement.

Specifications

  • Dimensions: 5 x 5 x 13.5 inches
  • Weight: 4.2 pounds
  • Filtration capacity: 1,600 gallons
  • Flow rate: 2 GPM
  • Filtration method: PP sediment filter (5 microns), advanced carbon block filter (0.5 microns)
  • Warranty:  1 year
  • Features: auto shut off switch, ⅜” hose, ⅜” to ½” water valve converter 

Things to Like

  • Great filtration performance – the Frizzlife MK99 successfully eliminates 99% of lead, chlorine (taste and odor), and sediments (sand, silt, and rust). VOCs, carcinogens, heavy metals (chromium 6, mercury), and turbidity are removed too. Many attested that the water is crisp and clean, and has a better taste.
  • Good filter life – the overall filtration capacity of the MK99 is 1,600 gallons which is quite decent as it can last 6 to 8 months before you need to replace the filter. It doesn’t clog quickly either. It remains effective up to the end of its lifespan.
  • The water flow rate is fast – the system can process 1.5 gallons of water per minute at 40 psi pressure and up to 2 GPM at 60 psi pressure which is pretty fast for an under sink water filter. There was minimal to no impact on the flow of water for most users. Some did notice a drop but they claimed it was still fast enough for normal usage – it takes a minute or less to fill an electric kettle.
  • Quick and easy to set up – it features the twist in/off installation design that makes the setup process straightforward and all the supplies needed to complete the installation are provided. It directly connects to the cold water line and can fit either ½” or ⅜” water valve.  
  • Simple filter replacement – it takes less than 5 minutes to do a filter change due to the twist-in/off design. You just twist off the cap, remove the old filter, insert the new one, and twist back the cap. Moreover, it’s only the internal filter cartridge that’s replaced, so the maintenance cost is less than most brands since you don’t have to change the whole unit (including plastic housing). 
  • Has a convenient auto shut-off valve – the filter cap has a built-in auto shut-off valve which gives you more control during filter changes. It automatically stops water flow through the filter immediately after detaching the cartridge. You don’t have to shut off the whole water supply to avoid flooding your home whenever you do filter changes.
  • Sturdy and compact construction – the filter housing and cap are solid plastic material. They won’t break quickly, plus the water hose and converter fitting are made of brass, hence they are equally sturdy and durable. The entire unit is also a compact single canister that can easily fit in tight spaces making it ideal for small kitchens that have under sink cabinets with limited room.

What not to like?

  • Only suitable for use with city water – the filter is effective but it isn’t suited for heavy-duty filtration needs. Bacteria, viruses, and other harmful contaminants present in totally untreated water such as well water don’t get removed. Large particles can easily clog the filter too causing the water flow and filtration process to slow down significantly. 
  • The water is initially cloudy and has an unpleasant aftertaste – there were reports that the water comes out cloudy after installation while others complained of an unpleasant salty taste at the beginning. The cloudiness clears up after running the water for a few minutes but some claim that the salty aftertaste takes a few days to disappear.
  • Several cases of water leaking out – water tends to leak a little around the connections at the filter and in the supply line itself. 

Final Remarks  

Overall, the satisfaction for this Frizzlife MK99 filter was high with regards to filtration performance, flow rate, and lifespan. It’s a wonderful option if you’re looking for an affordable under sink water filter for cleaning municipal water. You can consider it too if you have limited space in your under sink cabinet and want a compact unit that will fit in easily.

3. APEC WFS-1000 Under Sink Water Filter System

APEC WFS-1000 Super Capacity Premium Quality 3 Stage Under-Sink Water Filter System
  • High quality, designed, engineered and assembled in the USA; System built with US MADE super capacity filters for long lasting dependable filtration
  • Guaranteed to remove chemicals (i.e. chlorine), taste and odors. NOT designed for TDS removal
  • Premium long-lasting filters used to treat tap water, well water. Provide unlimited refreshing water

Specifications

  • Dimensions: 6 x 15 x 12 inches
  • Weight: 14 pounds
  • Filtration capacity: 12 months (gallon capacity is not specified)
  • Flow rate: 1 GPM
  • Filtration method: PP sediment filter, extruded carbon block filter
  • Warranty: 1 year
  • Features: a dedicated faucet, ½” x ⅜” male-female adapter, ½” x ⅜” female-male converter, ¼” x ⅛” male needle valve

Things to Like

  • Decent filtration performance – the 3-stage filtration process of the APEC WFS-1000 is quite effective at improving the taste and odor of water. It clears out all the chlorine as well as VOCs and other chemicals that affect the taste of water. It also gets rid of large particles including dust, rust, and sand. 
  • The filters don’t require frequent replacement – all three filters have a lifespan of 12 months and many attested that they do last that long. The quality of the filtered water only changes after the 12 months, so no premature filter replacements. This translates to lower maintenance costs considering also that you only change the filters and not the entire housing. 
  • Offers a fast and steady flow rate – there’s no significant change in the water flow. Most users mentioned that the water comes out of the faucet fast almost at the same rate as a regular tap. You can fill 6 large cups or glasses in just under a minute. 
  • Installation is fairly easy – there were no challenges reported when it comes to setting up this APEC filter system. All the equipment needed for the installation is provided and the filter holder even has pre-drilled holes to allow for easy mounting on a sidewall. However, the unit is large and heavy enough that it can sit on its own on the floor without mounting. Changing the filters isn’t hard either since they twist on and off.
  • The build quality is good – the unit has well-built parts that can last for years. The three filter housings are made of heavy-duty plastic material and are cleanly molded. The filter holder is equally a thick, sturdy plastic that won’t break quickly. The chrome-finished stainless steel faucet is also strong and tall which makes it simple to fill large pots or pans when cooking.

What not to like?

  • Not suitable for heavily contaminated water – this filter doesn’t remove fluoride, bacteria, viruses, cysts, chloramine, lead, or other heavy metals like arsenic. You can’t use it to filter densely contaminated municipal water or untreated water like well water. 
  • Cloudy water after installation – the water comes out cloudy when using the filter after installation. The cloudiness takes a few days or even a week to clear up. A few other users claimed that the water initially contains some particles from the carbon filters which also takes time to clear out.
  • Needs a bit more space under the sink – like the iSpring CU-A4, the APEC WFS-1000 is large and heavy because it features several filter cartridges. It can take up lots of space inside an under sink cabinet if it’s small leaving little room for storage of other items.  
  • Doesn’t work with the existing kitchen faucet – you can’t use this system with the standard kitchen faucet as it needs its dedicated faucet to draw the filtered water out. You have to install the provided faucet which may be a bit challenging if you don’t have an existing faucet hole already drilled on your sink or countertop.
  • The installation instructions aren’t clear – users complained that the instructions are a little confusing and it takes some time to understand which part goes where. 

Final Remarks  

The APEC WFS-1000 is worth checking out if your municipal water is already reasonably clean but you want to get rid of the chlorine residue and any other potential contaminant. 

4. Woder WD-S-8K-DC Under Sink Water Filter

Woder WD-S-8K-DC Water Filtration System - WQA Certified – USA Made Ultra High Capacity Direct...
  • ULTRA HIGH CAPACITY – WQA Gold Seal Certified 8,480 GALLONS - Notes: For longest life, use with municipal treated cold water only, not well water. Do not use with salty or softened water. Connects for use only with cold water for drinking.
  • USA MADE - NO PLUMBING REQUIRED – Comes with ‘Direct Connect’ hoses that fit standard 3/8” water valves under US kitchen and bathroom sinks. The 3/8” Direct Connect Hose are made to install directly to the existing cold water valve and faucet stem under your sink. Replacement filters ASIN B0144MFN92.
  • WQA GOLD SEAL CERTIFIED to NSF/ANSI 42 for Chlorine, taste, odor and NSF/ANSI 372 for lead free compliance as verified and substantiated by test data. Flow rate 2GPM @65 psig

Pros

  • Removes 99.99% of lead and chlorine
  • Removes also several other contaminants
  • Features a built-in swivel shut off valve
  • Easy to install and to replace the filter
  • Sturdy and durable overall construction
  • It’s backed by a 1-year warranty

Cons

  • Not suitable for use on well, softened, or salt water
  • The filter doesn’t last to its full capacity
  • The water flow slows down greatly over time
  • The connector can’t fit ½” water line 

Filtration Performance

The Woder WD-S-8K-DC model utilizes selective filtration technology to eliminate contaminants from the water. It’s a mixture of activated carbon and silver which have been grounded to microparticles and blended rather than layered.

This combination results in an effective filtration media which strains out 99.9% of chlorine and lead. The media also eliminates other heavy metals like mercury as well as VOCs, chromium 6, carcinogens, turbidity, and other contaminants. Users noted that the filtered water is free of cloudiness or foul chemical odors, and tastes much better.  

However, you can only use it on treated municipal water since it doesn’t remove most of the harmful contaminants in well water like bacteria, cysts, viruses, fluoride, and iron. It’s not suitable either for use with salty or softened water. 

Filtration Capacity and Flow Rate

The total filtration capacity is 8,480 gallons which is the largest on the list. Woder claims it can last about 3 years for a medium family of 4, but the filtration performance seems to decline gradually before the filter even reaches its full capacity. It gets clogged up with impurities over time which causes it to stop working after a year or two of regular usage. 

The water flow is fast (2 GPM) at the beginning such that you can fill a 12-cup mixing bowl within 45 seconds. However, it slows down over time (after one year) that it can take around 2 minutes to fill the same 12-cup mixing bowl.

Installation and Maintenance 

Setting up the unit was simple for all and it takes only a few minutes. No plumbing skills or experience required. It’s a single filter canister and it utilizes direct connect hoses that you simply screw directly onto the cold water valve. You won’t need a separate faucet too since it’s a direct connection and works with a standard kitchen faucet.

The downside is that it comes with only a ⅜” connector which won’t fit all water lines. If you have a ½” water line, then you will have to get an adapter in order to fit this filter onto it.

Changing the filter is simple and it has a built-in shut valve hence you don’t have to shut off the main water supply to the house when doing replacements. There’s no filter change indicator though which is disappointing especially because the filter is likely to become ineffective before exhausting its full capacity. 

The whole unit is solidly built. The hoses are heavy-duty and the metal connectors are all sturdy and durable. In terms of size, it’s a really compact system much like the Frizzlife MK99 filter – it doesn’t take up a lot of space under the sink.

Generally, this is a decent option if you need a simple but effective under sink water filter for removing lead, chlorine, and chemical contaminants from your tap water.  It’s also a better choice if you have a small countertop with limited space underneath the sink.

5. Culligan US-4-EZ-Change Under Sink Water Filter

Sale 28%
Culligan US 4 EZ-Change Sink Drinking Water Filtration System with Dedicated Faucet and Premium...
  • Provide your family with visibly clean, great-tasting water for drinking, cooking and more
  • Features: Reduces particulates class 1, chloride, cyst, chloroform, MTBE, mercury, lead, turbidity, perfluorinated chemicals; 0.5 GPM flow rate; Includes 1 twist-on/off filter cartridge replacement, tubing, dedicated faucet, and installation hardware
  • Compatibility: Culligan US-EZ-4 cartridges

Pros

  • Effectively removes most of the common contaminants
  • Doesn’t affect the water pressure of the main faucet
  • Installation and filter replacement is easy
  • Features an LED filter life indicator 
  • Backed by a 2-year warranty

Cons

  • Limited water filtration capacity
  • It has a low water flow
  • The plastic fittings crack quickly
  • It’s prone to leaking over time 

Filtration Performance 

The Culligan US-EZ-4 is a block filter made up of carbon and other composites which together work effectively to remove a majority of the common contaminants and chemicals in municipal water. They get rid of chlorine (97%), chloramine (98%), lead (99%), mercury (96.6%), cysts (99.9%), VOCs (99.8%), MTBE (96.9%) and turbidity (98%). 

Sediments are equally cleared out down to 0.5 microns as well as perfluorinated chemicals like PFOS and PFOA. You get very clear and clean filtered water that has no bad smell or odor. 

Filtration Capacity and Flow Rate

The filtration capacity is average at 500 gallons which means you’ll have to replace it after 6 months or less depending on your usage. The water flow (0.5 GPM) is slower compared to the other models and some mentioned that the filter gets clogged quickly causing the flow to reduce drastically to almost 0.1 GPM – it can take over 10 minutes just to fill a one-gallon jug. 

Installation and Maintenance

Installation is a simple process since it’s a single filter canister that uses twist-on and twist-off mechanisms as well as quick-connect fittings. It comes with only a ½” fitting, thereby you’ll require an adapter in case your sink has a ⅜” shutoff valve. 

The filter can’t work with a standard kitchen faucet but it comes with a dedicated faucet which means you’ll have to drill a hole on the sink if you don’t have one already drilled. The unit is compact hence it will fit easily in limited under-sink space. 

The replacement process is fast and straightforward due to the twist-on and twist-off mechanism. Moreover, there’s an LED filter life indicator on the head of the filter that notifies you when a filter change is needed. 

One major downside though is that the fittings are made of plastic instead of brass. Many reported that they crack quickly even on hand tightening when setting it up. Others mentioned that they develop a slow but steady leak after installation which ends up damaging the cabinet overtime. 

In general, this is an effective water filter and it comes at an affordable price making it a decent option if you are looking for a budget under sink filter or if you’re tight on space. 

6. Filtrete 3US-PS01 Under Sink Water Filter

Sale 42%
Filtrete Advanced Under Sink Quick Change Water Filtration System 3US-PS01
  • HEALTHY LIVING FILTRATION LEVEL - This system reduces chlorine taste & odor as well as microbial cysts
  • EXTREMELY CLEAN WATER - This system reduces sand, sediment, rust, and soil (0.5 microns)
  • USES EXISTING FAUCET - Filter water right at the sink without having to install an entirely separate faucet

Pros

  • Effective at removing chlorine, cysts, and sediments
  • Simple to install and to change the filter
  • Doesn’t need a dedicated faucet
  • It can fit in small under sink faucets
  • It has a one year warranty

Cons

  • Not suitable for use with untreated water
  • It doesn’t last the full 6 months 
  • Water flow is very slow 
  • The water line fitting rounds off easily

Filtration Performance

This is a much more basic filtration system that seems to do it’s work well. It uses a carbon block filter which gets rid of chlorine taste and odor from the water as well as microbial cysts and most of the sediments.

The filtered water has no smell or odor but it doesn’t come out clear at the beginning. Several users claimed that black carbon particles are left on the bottom of the glass or water bottle.

Filtration Capacity and Flow Rate

The Filtrete 3US-PS01 is rated to process up to 2,000 gallons of water or last 6 months before needing replacement. Unfortunately, most people said it only lasts 3 to 4 months with normal use. The specified flow rate is 1.5 GPM but this too doesn’t match up as there are many claims that it suddenly reduces by about 50% after a month of normal use and continues to slow down afterward to the point that it takes more than a minute to fill a glass of water. 

Installation and Maintenance 

You won’t have any difficulty setting up this filter. Users found the process easy since it uses push-in fittings. It doesn’t require a dedicated faucet either – it connects directly to the cold water line and the kitchen faucet. The problem is that it fits just ⅜” water shut-off valve, so if yours is of different size, then you’ll have to buy a converter to connect the system.

The whole unit is low-profile enough to install in under sink cabinets with less-than-average space. You won’t have a hard time replacing the filter too as it takes just a single quarter turn to release it. 

The filter itself is solidly built but the water line fitting is made of a cheap plastic material. It tends to round off easily which can cause the hose to blow off the valve leading to water gushing out and flooding the cabinet or the kitchen. 

Besides that, you have to let a lot of water flow through the filter and go to waste during the initial installation to flush out all the carbon particles. 

Overall, the Filtrete 3US-PS01 is a basic under sink water filter that’s a more suitable option if you are after just removing sediments and chlorine taste and odor from the water.  

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