Best Under Sink Water Filters
Under sink water filtration systems are an affordable and effective way to provide clean, safe drinking water to your kitchen sink without having to install a whole home unit or refill a pitcher all the time.
But with all the technical jargon and confusion around water filters, manufacturer claims, and contaminant removal it can be such a pain in the ass to find the correct unit for your water.
For example, with under counter filters you need to decide if reverse osmosis filtration or standard carbon filtration is best for your water situation.
No need to worry. We have spent countless hours researching, talking to manufacturers & customers, and testing different filters to determine which models are the best.
In this review, we will outline the top under sink filters on the market, and explain why they made the cut. That way you can be sure you’re choosing the right device for your home’s water needs.
Table of Contents
- 1 Top 10 Under Sink Water Filtration Systems
- 2 Criteria to Consider When Buying an Under Sink Filter
- 3 Best Under Sink Water Filter Reviews
- 4 Under Sink Water Filter Buyer’s Guide
- 5 What is an Under Sink Water Filter?
- 6 How Do Under Sink Water Filters Work?
- 7 Why Use an Under Sink Water Filter?
- 8 Under Sink vs Countertop Filters
- 9 Under Sink vs Whole House Water Filter
- 10 Installation and Maintenance Suggestions
- 11 Conclusion
Top 10 Under Sink Water Filtration Systems
#1 Clearly Filtered 3-Stage
#2 Waterdrop G3
#3 Aquasana OPTIMH20
#4 Pelican 3-Stage
#5 Aquasana 3-Stage Max Flow
#6 Waterdrop 3-Stage Black
#7 ECO Soft 3-Stage
#8 iSpring RCC7AK
#9 CuZn UC 200
#10 APEC WFS 1000
Criteria to Consider When Buying an Under Sink Filter
When deciding between two or more cars to buy, you’re usually comparing the same features on each – mileage, age, price, gas efficiency, etc. With under sink water filters, these are the criteria we considered and that you need to consider when deciding which one to go with: contaminants removed, filter lifespan and replacement, flow rate, pure water to waste water ratio, certifications, relative price, and ease of installation.
The main purpose in purchasing an under sink filter system is to filter out the contaminants in your tap water supply. So, you need to make sure it can remove the specific impurities you’re dealing with.
The specific contaminants that a filter can remove varies from model to model, but in order for water to be deemed suitable for drinking it must meet these standards at the very minimum.
In under sink filter systems, the most common types of filters used are carbon, reverse osmosis, and ion exchange. The specific types and number of filter stages will determine exactly what the unit can remove.
|Common Filter Types in Under Sink Units||Contaminants Removed|
|Carbon (Block or Granular)||Chlorine, taste and odors, asbestos, lead, mercury, VOCs, trihalomethanes, disinfection byproducts, some microorganisms|
|Ion Exchange||Minerals (calcium, magnesium), barium, radium, heavy metals|
|Reverse Osmosis (Most Effective)||Most microorganisms, minerals, heavy metals, suspended particles, fluoride, arsenic, nitrates, hexavalent chromium, perchlorate, VOCs, most radionucleotides|
Filter Lifespan & Replacement
Under sink water filters are generally designed so that you replace the filter cartridges every so often. This should usually be doable without a plumber, and most filters should be replaced every 6-12 months. The type of filter, how much you use it, and the amount of contaminants in your water (which you should have determined already) will be the main things that affect your filter’s lifespan.
Overall, you want to look for a filter system that is durable and which you can easily replace only once every 6-12 months if possible.
Pure Water to Waste Water Ratio
Reverse osmosis style filters use water to flush away the contaminants they filter. This water has a higher contaminant concentration and is considered non-potable (meaning it isn’t fit for drinking). On average, reverse osmosis filters use four gallons of wastewater for every gallon of fresh water generated, and systems that can minimize this waste are ideal.
When comparing the price of under sink filters, there are two main things to take into consideration: the cost of the system and its initial installation, and the cost of the replacement cartridges.
For example, you see a system that costs only $150, but it needs a plumber to install for $100 and the cartridges are $150 to replace yearly. At the end of five years, you’ll have spent $1,000.
On the other hand, you may see a system that costs $400 up front but doesn’t require a plumber for installation, and the cartridges are only $75 per year. If you go with this one, even though it’s more up front, at the end of five years you’ll have only spent $775. Don’t forget to look at the long-term costs and savings of the systems you’re considering as well as the quality of filtration.
Something else to consider is the effect that filtration has on your flow rate. Flow rate is measured in gallons per minute or gpm, and it describes your faucet’s water pressure or how fast it comes out. One of the biggest complaints people have about their under sink system is how it negatively impacts the flow rate.
There’s usually a trade-off between level of filtration and flow. Reverse osmosis filters have a notoriously low flow rate – but that’s because they filter out the smallest particles. An ion exchange filter has a higher flow rate, but it doesn’t remove the same amount of contaminants.
The best under sink water filter will meet the quality standards you need for your water while still maintaining a functional flow.
There are two independent, 3rd-party associations that certify water filters – the National Sanitation Foundation (NSF) and the Water Quality Association (WQA).
If a product is certified by either the NSF or WQA, it’s an extra assurance that the filter meets high quality standards. Reverse osmosis filters, for example, may be certified for the NSF/ANSI 58 standard which evaluates things like the filter’s structural integrity, efficiency, contaminant reduction performance, and other criteria.
A carbon block under sink filter, on the other hand, may be certified for the NSF/ANSI 53 standard, which evaluates the filter’s ability to remove materials with detrimental health effects.
For more information about water filter certifications, click here.
Ease of Installation
This is an often-overlooked factor when it comes to buying an under sink water filter, and one which you won’t usually find reliably described on the box.
The cost of engaging a professional plumber to install an under sink filtration system is certainly going to outweigh any savings gained by opting for a cheaper unit. While most manufacturers will downplay the complexity of installation, only first-hand user experience from customer reviews will give you a true picture of the ease with which a filter is installed.
Best Under Sink Water Filter Reviews
1. Clearly Filtered 3 Stage
Our #1 recommendation for an under sink water filter is the Clearly Filtered 3-stage under sink filter system.
It removes the most contaminants of any residential filters, it’s NSF certified, you can install it yourself, and it comes with a lifetime warranty.
Clearly Filtered is also one of the top brands in the water filtration market – and for good reason. They have a history of producing superior products that deliver quality results, and this product is a prime example.
How it Works
The three stages of water filtration consist of:
- Premium carbon priming filter (granulated coconut carbon removes chlorine, tastes, odors, cloudiness, and colors)
- Heavy metal and VOCs Filter (removes 99% heavy metals, pesticides, herbicides and more)
- Fluoride & arsenic filter (removes 99% of fluoride)
Main Features & Benefits
Contaminants removed: This filter removes 99.7% of 232+ contaminants – more than any other system on the market.
Contaminants removed include: fluoride, chlorine, perfluorinated chemicals, pharmaceuticals, herbicides, semi-volatile compounds, heavy metals, VOCs, radiological elements, pesticides.
You can Click here to see all of Clearly Filtered’s test results.
Filter lifespan and replacement: One of the best things about this filter is that Clearly Filtered offers a lifetime warranty on it, so even if something goes wrong you can rest easy knowing there won’t be any extra expense. Otherwise, this filter has a 2,000-gallon filter life and is made with stainless steel hoses that offer extra durability.
Flow rate: Several customers have reported that this filter cuts your faucet’s cold water flow rate roughly in half. Compared to many reverse osmosis filters, however, you get a higher flow rate than you would with those while still achieving the same level of water purification. Not to mention, there’s no waste water, either.
Certifications: Clearly Filtered systems have been NSF certified.
Price: While the $500 price tag may cause some sticker shock, you instantly get $100+ back in the installation. This filter is able to be DIY installed in 15 minutes or less without a plumber. The simplicity of installation can’t be overstated, which also makes it the perfect solution for renters because it’s easy to remove and not permanent.
Another thing to consider with the price is the lifetime warranty. While you might have to pay $250 for one system now and another $250 when it breaks in 10 years, you can rest assured that Clearly Filtered has you covered.
At $400 every 9-12 months, the replacement cartridges aren’t cheap either. When you compare them to the other under sink systems at a similar price point, however, you’re paying the same amount for higher-quality water.
- Filters out 99.7% of 232+ contaminants
- Lifetime warranty
- Top of the line 3 stage filtration
- Super easy to install and replace
- Filter life 2,000 gallons
- Just as good or better as a system with RO
- NSF certified
- Sleek design – doesn’t take up much cabinet space
- Not cheap but worth it for lifetime warranty and quality
- 50% reduction in flow rate of the cold water line
2. Waterdrop G3
Coming in at #2 is the Waterdrop G3 reverse osmosis under counter system.
This is one of the most powerful under sink filters with an impressive 400 gallons per day capacity, which would suit even a large household. The powerful reverse osmosis system removes 99% of TDS, it’s NSF certified, and it fits nicely under your sink.
Waterdrop is becoming a top brand in high-quality innovative water solutions.
How it Works
The Waterdrop G3 has a 7 stage filtration system, making it one of the most effective and thorough systems on the market. These are the following stages and components:
- Pre-sediment and carbon block filter (made from granulated coconut with PP cotton, removes sediment and cloudiness, chlorine, and other bad odors and tastes)
- 3-stage reverse osmosis filter (DOW reverse osmosis system has a 0.0001 micrometer pore size to filter out even the smallest contaminants)
- Post-activated carbon block filter (refines taste, odor, and color)
Main Features & Benefits
Contaminants removed: The Waterdrop G3 removes 99% of total dissolved solids in your water using the reverse osmosis system.
Contaminants filtered include chlorine, foul tastes and odors, suspended particles, limescale and other minerals, heavy metals, microorganisms, and other harmful contaminants.
Filter lifespan and replacement: Depending on your household size/water usage and the amount of contaminants in your water, each set of carbon cartridges should last you 6-12 months while the RO cartridge can last up to 24. This under sink system also comes with a one year warranty to protect against manufacturer defects.
Filter replacement is easy and only takes about 3 seconds (twist and pull), and the filters are available online. The integrated composite filter not only enhances the filtration performance but also reduces the number of cartridges. This will bring to a lower replacement cost and easier maintenance.
Flow rate: This filter system has a flow rate of 400 gallons per day, which means it takes roughly 12 seconds to fill a cup. While this may seem like a low flow rate, it’s faster than many other reverse osmosis filters on the market.
Fresh to waste water ratio: Unlike traditional RO systems, this filter has a 1:1 drain ratio. Many people are concerned about the amount of waste water a RO system produces, but the G3 system has a low drain ratio meaning that for 1 gallon of purified water, it only produces 1 gallon of waste water.
Certifications: This product has been NSF certified for 400+ chemicals.
Price: The initial system may set you back a bit at $545, though the good news is that you don’t need a plumber to install it. After that, you can replace all three cartridges for under $135 so you do end up spending less in the long run than some other models.
- 7-stage filter removes 99% of contaminants
- Uses reverse osmosis filtration
- Largest capacity & most powerful system
- Compact, tankless design that fits well under sink
- 400 gallons per day flow rate
- Designed for DIY, this system is very simple to install
- One of the more expensive models, but it’s worth investment and the replacement cartridges aren’t too pricey
3. Aquasana OPTIMH20 RO+ Claryum
Our #3 pick is the Aquasana OPTIMH20 reverse osmosis and claryum filter. This filter also utilizes reverse osmosis but is more sparing on your flow rate. It removes over 87 contaminants, is NSF certified, and is a more budget-friendly option.
Aquasana is another one of the leading brands in the water filtration market and they produce reliable, top-quality products that you can rely on to get your clean, pure, and tasty water.
How it Works
This model from Aquasana is also a reverse osmosis system, and it incorporates six different stages of filtration to remove over 89 different contaminants:
- Reverse osmosis filter (removes dissolved particles smaller than 1 micron such as arsenic and fluoride)
- Activated carbon filter (acts on organic chemicals and VOCs like pesticides)
- Catalytic carbon filter (removes chlorines and chloramines)
- Ion exchange filter (binds heavy metals in the water)
- Absolute sub-micron filter (removes protozoa cysts and asbestos)
- Remineralization (adds healthy minerals back into the water to make it more alkaline)
Main Features & Benefits
Contaminants removed: This model from Aquasana provides premium filtration technology with reverse osmosis. It’s tested and proven to remove fluoride and 87 additional contaminants.
Filter lifespan and replacement: You can expect the RO membrane and the remineralizer to last roughly a year before they need to be replaced, and the other cartridges have a 6-month lifespan on average. The cartridges are very easy to replace, and the under sink system itself comes with a 90 day guarantee and a 2 year warranty.
Flow rate: Compared to the Waterdrop G3, this filter has a flow rate of 720 gallons per day or 0.5 GPM. The heightened flow rate is due to the larger pore size of the RO membrane, so while the Waterdrop filter removes more contaminants this one maintains pressure better.
Fresh to waste water ratio: Like most RO filters, this system generates four gallons of waste water for every gallon of water purified.
Certifications: Aquasana conducts rigorous testing on their products, and this model is certified to NSF/ANSI standards so you can be certain it is effective.
Price: This filter normally runs you $307 to purchase, but it does require drilling into the freshwater piping to install so it is recommended that you have a plumber do it. The good news is that the replacement cartridges only cost about $65 each.
- Rigorously tested and certified to NSF/ANSI standards to remove 87 contaminants including fluoride
- 6 stage filtration system with reverse osmosis
- Reliable and trustworthy brand you can count on
- More affordable price point
- 0.5 GPM flow rate
- Remineralization stage for better taste and alkalinity
- Needs a plumber to install
- High waste water to fresh water ratio
4. Pelican 3 Stage
Our #4 choice is the PDF-1000VF under counter filtration purification system by Pelican Water.
Pelican Water is an established and trustworthy brand, and you can count on them to deliver a system that provides clean and tasty water. This system has a 1,000 gallon capacity, doesn’t generate waste water, and contains a metered flow control.
How it Works
This pelican model is a 3-stage filtration system that utilizes both GAC and mechanical filters.
- 25-micron mechanical pre-filter (removes sediment and large dissolved particles)
- Two catalytic GAC filters (removes chemicals causing bad odors and tastes including chlorine as well as microorganisms)
Main Features & Benefits
Contaminants removed: This system removes 99% of bacteria, cysts, viruses, chlorine, lead, and particulates.
Filter lifespan and replacement: The filter cartridges last from 6-12 months on average, and the system has a 1,500 gallon capacity. Pelican also offers a one year manufacturer warranty on their filter.
Flow rate: With a 1 GPM flow rate, you can rest assured that you’re not compromising on your pressure to get clean water.
Certifications: This product is IAPMO certified to the NSF/ANSI standards.
Price: The base price of this filter is $185, and the cartridges are $80 to replace total. The price makes this system a budget-friendly solution for those who want to upgrade their water quality without breaking the bank.
Keep in mind that you will need a plumber to install this system, however, because it requires fittings that are not standard in most home piping.
- Removes 99% of contaminants
- Rigorously tested and certified to NSF standards
- Trustworthy and reliable brand
- Affordable price point
- 1 GPM flow rate
- Additional plumbing fittings needed for most installations
- Awkward to fit under the counter
5. Aquasana AQ5300 3-Stage Max Flow
This 3-stage filtration system from Aquasana has all of the features you’d expect from an under sink filter, at a truly affordable price and from a leading brand.
How it Works
Unlike their RO filter, this Aquasana product utilizes a multi-stage carbon filter with claryum to achieve purified water.
- Activated carbon filter (removes organic chemicals and VOCs like pesticides and some pharmaceuticals)
- Catalytic carbon filter (reduces chlorine and chloramines)
- Ion-exchange filter (works on lead, mercury, and other heavy metals)
- Absolute sub-micron mechanical filter (removes asbestos and microorganism cysts)
Main Features & Benefits
Contaminants removed: Reduces or removes 77+ contaminants with its 3-stage system.
Filter lifespan and replacement: The filter cartridges are good for 800 gallons and need to be replaced every six months, and the main system itself comes with a one year warranty and has a 90 day guarantee from the manufacturer.
Flow rate: Because this model uses a multi-stage carbon system instead of a reverse osmosis filter, the flow rate is a moderate 0.5 GPM.
Certifications: This product has been NSF/ANSI certified for multiple standards.
Price: The price of the under sink system itself is $245, and the replacement cartridges are $80. That makes this product a good middle-of-the-road option for those who want to ensure water quality.
- 77+ contaminants removed
- Tool-free filter change
- Simple installation – good for DIYers
- 0.5 GPM flow rate
- Faucet included with the system
- NSF certification
- Some wear items (such as seals and o-rings) will not last as long as competing models
Bottom Line: This is one of the budget choices we included on our list. Despite its cheap price, this water filter is capable of producing clean and crisp water, just like the more expensive models. The faucet is also available in a range of finishes so you can be sure it will fit into your existing décor.
6. Waterdrop 3 Stage Black
Our #6 pick is the Waterdrop 3 stage ultra filtration under sink system.
Waterdrop’ s version of the carbon filter has several advantages including an integrated waterway and an indicator system that lets you know when the filters need to be changed.
How it Works
The Waterdrop ultra filtration system does not require an under-sink electricity supply and produces quality purified water with zero waste water. It uses the following stages:
- PP Sediment filter (removes large suspended particles like sand, rust, etc)
- Ultrafiltration filter (mechanical filter that blocks particles larger than 0.1 microns)
- Carbon block filter (reduces most of the chemicals causing bad odors and tastes as well as heavy metals)
Main Features & Benefits
Contaminants removed: The ultrafiltration membrane has a pore size of 0.01 micron, so combined with the other stages it can filter out most of the contaminants in water.
This filtration system does not remove TDS (total dissolved solids), which means that minerals like calcium, magnesium, potassium, sodium, etc stay in the water.
These electrolytes aren’t bad for you, but they contribute to making water “hard”. To achieve soft water, you can either add a softener system or get a reverse osmosis system that will remove the TDS.
Filter lifespan and replacement: The sediment filter lasts 6 months, the carbon block filter lasts 12 months, and the ultrafiltration filter lasts up to 24 months before needing to be replaced.
It also has a cutting edge integrated waterway to prevent water leakage, which allows you to replace the filters without cutting off the water supply.
Flow rate: Like most non-RO filters, this model has a flow rate of roughly 0.5 GPM.
Certifications: Unlike the other products, this model has not been certified by the NSF or WQA.
Price: At $175 to install and $166 to replace the filters yearly, this is another great low-cost solution for your water filtration needs.
- Low cost and high quality system
- Innovative technology
- 3-stage quality filtration
- Sleek good looking design that fits nicely under sink
- Easy to install and maintain
- Not as powerful as their G3 model
- Does not reduce TDS
- Smaller capacity than the G3
7. Ecosoft 3-stage High Capacity
Ecosoft’s 3-stage tankless under counter water filter was a real surprise for us and snuck into the top 10.
This gem doesn’t have a big-name brand behind it, but the quality of water it produces certainly earns it a place on this list.
How it Works
This 3-stage filtration system is made with the following components:
- Sediment filter (filters out large particles and suspended material)
- Ecomix filter (reduces ammonium, organic matter, minerals, iron, and manganese)
- Carbon block filter (removes organic chemicals and VOCs as well as many heavy metals)
Main Features & Benefits
Contaminants removed: This filter removes heavy metals, chlorine, sediment, and reduces manganese and iron levels too. The Ecosoft filters scale-causing minerals like magnesium and calcium, softening the incoming water as well.
Filter lifespan and replacement: This filter system is a little different in that they recommend their cartridges be replaced every 6 months, and there is a built-in pressure gauge that will give you a heads up when that time is coming.
Flow rate: The flow rate is slower than some of the other filters on our list, which is a downside.
Certifications: This product is not certified by either NSF or WQA.
Price: The price for the system is $99, and while the cartridges need to be replaced every 6 months they are only $20.
- Affordable setup kit and filters
- Faucet included
- Easy installation
- Very affordable budget option
- Lower flow rate
Bottom Line: Everything you need for installation comes in the box, and fitting is simple enough for most competent people to carry out themselves in under an hour. Although the low flow rate is a drawback, this is another good budget option if you’re not willing to invest in one of the top picks.
8. iSpring RCC7AK
Coming in at #8 is the iSpring RCC7AK model.
This model has 6-stage filtration with alkaline remineralization and it is a reverse osmosis system. Many users have reviewed this product, and the overall consensus is that it is one of the top reverse osmosis under sink models at an affordable price.
We also did a full iSpring filter review if you want more information about the company.
How it Works
This filter has top of the line RO filtration technology. It is made of the following stages:
- 5-stage RO filter (uses standard reverse osmosis to remove over 99% of contaminants)
- Remineralization filter (adds electrolytes back into the water to add a pleasant taste and alkalinity)
Main Features & Benefits
Contaminants removed: This system removes 99% of total dissolved solids, chemicals, and VOCs including fluoride, asbestos, arsenic, etc.
Filter lifespan and replacement: The filters should be replaced every 6 months roughly, and both replacement and installation are easy DIY projects.
Flow rate: At 75 gallons per day, this filter has a flow rate that is more like you would expect from a RO under sink system.
Waste water to pure water ratio: This system produces three gallons of wastewater for every gallon of water purified, which is slightly better than the average for RO filters.
Certifications: This product has been NSF certified.
Price: The initial cost for the under sink system is about $198, which is less than you’ll pay for most other reverse osmosis systems. For a year’s supply of replacement filters it’s $62.
- 6 stage filtration using reverse osmosis
- Good customer service
- Good overall customer feedback
- NSF certification
- Wastes more water than a non-RO option
- Bulkier and takes up more space under sink
- Low flow rate
Bottom Line: Overall, if you’re looking for a reverse osmosis under sink option this is another good product to consider.
9. CuZn UC-200 Under Counter Water Filter
With an average 4.8 star rating from almost 1,500 Amazon reviews, it would be fair to say that the UC-200 is a popular under sink water filter…and 91% of reviews rate it as five star.
We also reviewed this unit in full detail at our CuZn UC-200 review.
How it Works
This product incorporates several different filtration components to purify your water:
- Microsediment membrane (reduces the amount of smaller suspended particles)
- KDF-55 filtration media and catalytic carbon filters (remove heavy metals, VOCs, organic and inorganic chemicals, bad tastes and odors)
Main Features & Benefits
Contaminant removal: The UC-200 doesn’t actively soften water and is unsuitable for use with well water, but it provides outstanding results when used with municipal water supplies. The unit inhibits bacterial and mold growth whilst providing excellent filtration of chlorine, pesticides, heavy metals, sediment, algae and bad tastes and odors.
Filter lifespan and replacement: Connecting directly to your existing faucet, this unit has a filter rated to last for 5 years – that’s a pretty long time.
Easy to install, the unit doesn’t require the installation of an additional faucet and requires virtually no maintenance. The only downside is the unit’s size, which is quite bulky although still small enough to fit within your existing kitchen cabinet.
Flow rate: This product’s flow rate is not available but there are no customer reviews stating that there has been a significant reduction in pressure.
Certifications: This product has been NSF certified.
Price: One of the main appeals of this filter is its cost over time. Its longevity means that you’re not going to pay as much for this system as other traditional under sink systems. There’s also a five year warranty on each filter that ensures it matches its life expectancy.
- Excellent filtration
- Very long filter life
- Responsive customer support
- Larger than other under sink filter units
- Does not reduce TDS or PPM meter readings
Bottom Line: Overall, you can get great value from this popular filter and still remove most contaminants.
10. APEC WFS 1000
Last on our list at #10 is the APEC WFS 1000 model. This honorable mention is another budget option that offers good filtration at an affordable price.
Overall, APEC is a solid brand in the water filtration market that competes with our top picks.
How it Works
This under sink system uses a 3-stage system to filter out impurities similar to many of the other filters on our list.
- High-capacity polypropylene sediment (removes suspended particles like dust, sand, and rust)
- Carbon block filter (takes out chlorine, bad tastes and odors, VOCs, and other chemicals)
- Second carbon block filter (further refinement and filtration of the same contaminants)
What Makes it Stand Out
Contaminants removed: It’s guaranteed to remove chemicals, taste and odors and has a 3 stage filtration system with 2 super-capacity carbon blocks and a super-capacity sediment filter.
Filter longevity and replacement: While this filter system isn’t as durable as some of the others, it does come with a 1 year manufacturer warranty and the cartridges last for roughly a year.
Flow rate: This model boasts a higher flow rate than some of the other filters.
Certifications: This filter has not been NSF or WQA certified.
Price: For the main system the price is $139, and the replacement cartridges run about $45 per year to change out.
- Affordable price
- Effective filtration
- Made in USA
- Not as effective as our top picks
- Brand is not as reputable
- Just ok
Bottom Line: Overall, this model does not match our top picks for filtration or product quality, but if you’re looking for an average budget option then it’s worth a look. This product is also made in the USA, it’s earth friendly, and easy to install.
Under Sink Water Filter Buyer’s Guide
As with most water filtration products, it can be easy to get washed away in a flood of technical jargon and confusing comparisons.
Lucky for you, we’re here to help.
Our guide aims to simplify these handy systems so that you know what’s important and what’s not, and give you the tools to decide which is the best under counter water filter for your home.
What is an Under Sink Water Filter?
An under sink water filter is a filter which is installed beneath a sink (usually in the kitchen) and connects to the incoming water supply.
Water passing through the filter is purified and delivered from the faucet with higher quality and fewer contaminants, tastes and odors.
These units are usually best for people looking for just drinking water filtration and who aren’t as concerned with having all their water filtered.
How Do Under Sink Water Filters Work?
Most under sink filters use a combination of activated carbon filters and pre-filters to trap sediments and organic materials within the incoming water supply as well as reverse osmosis membrane filtration. Filters or casings can be bacteriostatic or are often given an antimicrobial coating to prevent mold and bacteria growth within the filter.
UV filtration and KDF filters are also often used in under sink models. To learn more about these types of water filters and others, click here.
Different Types of Under Sink Water Filters
There are 3 defined types of under sink water filters: Conventional, Simple and Reverse Osmosis. The differences between each have been described below.
Conventional under sink water filters connect into the existing cold water line to the sink and feed a separate faucet (usually included with the filter kit). These systems can be more complicated to fit – owing to the plumbing amendments required to accommodate the tee which feeds the new filter.
Filter lifespan in a conventional system is usually improved, as the filtered water is drawn off separately from the main cold feed from the existing faucet.
Simple under sink water filters are fitted in line to the cold water supply to your existing faucet. This minimizes complications when installing as fewer plumbing changes are required, and it also removes the need to drill through your countertops and fit the additional filtered faucet.
Simple water filtration systems tend to require replacement filters more regularly because they are filtering all water that goes to the faucet. This causes a significant increase in the wear and tear on the filter in a busy home.
Reverse Osmosis (RO) filters work differently from other filtration systems.
Most other filters use the incoming water pressure (either pumped from a well/borehole or from a municipal supply) to push feed water through the filtration devices designed to trap sediments, destroy organic particles such as bacteria, and filter out contaminants like pesticides and heavy metals (depending on the model).
RO uses pressure across a semi-permeable membrane to force pure water to one side of the membrane while contaminants remain on the other. This results in a volume of purified water which is stored in a tank for use at the faucet, and a concentrated brine mixture containing all of the contaminants, which is then flushed away as waste.
The nature of the flushing process means that a significant volume of water is wasted with RO systems, and the need for pre filters and a storage tank results in a bulkier system needing to be situated below the sink.
Why Use an Under Sink Water Filter?
There are many benefits to using an under sink water filter in your home:
- Improves taste of drinking water
- Removes contaminants which can cause short-term and long-term illnesses
- Takes up very little space
- Very affordable way to improve water quality
- Saves money on buying bottled water, as well as plastic waste
- Easy to install without a plumber (depending on the model)
The reality is that water quality is becoming more widely discussed in America, and catastrophes such as those seen in Flint, Michigan have made more and more people aware of potential contaminants within their water supply.
Many people take a “safety first” approach and install some form of water filtration to improve their tap water and reduce the risks posed by poor water quality. Under sink water filters are a simple, cheap and reliable way to achieve this.
Under Sink vs Countertop Filters
You may be wondering if you have other options besides an under sink water filter, and the answer is yes. You can also look at getting a countertop filter, and we’ll take you through the pros and cons of both.
Under Sink Filter Pros and Cons
- Hidden within cupboard unit
- Easily accessed for filter changing and maintenance
- Provide effective filtration to dedicated or existing faucet
- Wide range of models available
- Cheaper than whole house filtration systems
- Easy to fit
- Only filters water to one outlet
- Can be awkward to install depending on cupboard size
- Can take up space in cupboard
- Leaks can go unnoticed
Countertop Filter Pros and Cons
- Easy to access for maintenance and filter changes
- Leaks are obvious as unit is in full view
- Slower filtration rate
- Take up space on kitchen worktop
Under Sink vs Whole House Water Filter
Rather than just filtering water to your kitchen sink, you can have a whole-house filter installed that will purify all the water coming into your home. These are the factors to consider when making a decision between the two:
Whole house filtration systems are more expensive to purchase than undersink water filters and are usually installed by qualified professionals. The installation cost alone of a whole house water filtration system will usually be more than the outright cost of an undersink filter.
While whole house filters are usually installed in the basement and connected to the main incoming water supply, under sink water filters are installed directly below one water outlet.
This means that when using a whole house filtration system, all water through all of the outlets in the property is filtered including dishwashers, washing machines and showers whereas an under sink filter system only filters water to one faucet.
As they usually treat more water, it is common for whole house filtration systems to require either more regular filters changes, or the filters are more expensive to buy outright when compared to under sink water filters.
Whole house filtration systems are capable of filtering large volumes of water instantaneously while under sink filters can take time to fill just one glass.
If you can afford to install a whole house water filtration system, they are a great option for providing clean, pure water to all areas within your home.
Keep in mind that whole house systems are best for people who want all of their water filtered including to their showers, sinks, washing machine, and more.
On the other hand, remember that a lot of our top under sink picks also contain reverse osmosis filtration which a lot of the whole house systems do not contain. This means with an undersink unit for drinking water you can get a purer level of water compared to a whole house filter.
In summary, if you just care about your drinking water then sticking with an undersink filter is your best bet. If you care more about all the water in your house then it’s best to check out our whole house units or even consider combining a whole house system with an undersink system for the most comprehensive level of filtration.
You can see our best whole house filter systems here.
Installation and Maintenance Suggestions
How to Install an Under Sink Water Filter
The installation method will vary according to the model of under sink water filter that you purchase and you should always follow the manufacturer’s instructions. However, fitting the units will usually follow the same steps:
- Isolate your water supply and switch on the tap until any excess pressure and water has drained.
- If your filter has a dedicated faucet, fit this to the countertop by drilling a hole in the desired position and inserting the stem. Secure using the fixings provided.
- Fix the filter body below the sink in the kitchen cabinet.
- Connect the existing cold water feed to the new filter. If using a simple under sink filter, this will connect in line to your existing tap. If using a conventional filter, you will need to cut a tee into the cold water feed, then connect one side to the existing faucet pipework and the other side to the new filter.
- Connect and tubing and ensure joints are tight.
- Close the taps and slowly switch the water back on.
- Reopen the taps to vent any air from the cold water pipes – switch off again once water runs through normally.
- Check all joints for any sign of leaks.
- Flush the filter through as directed by the manufacturer, usually for 5-10 minutes
- Your under sink water filter is ready to use!
When Do You Need to Change the Filter Cartridge?
The manufacturer will always include guidelines for the expected cartridge filter life within the product literature however as you get used to using your under sink water filter you may notice some early warning signs that the filter is coming to the end of its life.
Flow rate is reduced
This can be a sign that the tiny pores within carbon filters are bec
The manufacturer will always include guidelines for the expected cartridge filter life within the product literature. However, as you get used to using your under sink water filter, you may notice some early warning signs that the filter is coming to the end of its life – such as a lower flow rate and change in taste.
Changes to Taste
As a filter becomes clogged with contaminants removed from the water supply it will begin to allow some particles through that would otherwise have been filtered – these will affect the taste of the water at the faucet.
Low Flow Rate
This can be a sign that the tiny pores within carbon filters are becoming blocked as they reach capacity or that the RO membrane is becoming more permeable. Check that all valves are properly open but if the flow rate to other outlets is unaffected, it is time to buy a new cartridge.
As mentioned, manufacturers will always publish the recommended filter life, usually in the format of both gallons of water filtered and time installed. You should always pay attention to these figures (even if you have to estimate the usage) – manufacturers spend thousands of dollars testing their products for quality and these limits are published according to the findings. These values are usually the point when the quality of filtration begins to decline.
How to Clean and Replace Cartridges
Cartridge replacement will vary from model to model and will be detailed specifically by the manufacturer in the product manual. These are the general steps you will take:
- Switch off the water supply and open the faucet to relieve any pressure and drain water from the line. If there are isolation valves on the pipework on either side of the filter, close these too.
- Using a tool if required, open the filter housing – this will usually twist off using a wrench or special tool supplied with the filter.
- Remove the old filter cartridge.
To Clean the Cartridge
- Close up the filter housing without the cartridge. Switch on the water supply and rinse the cartridge thoroughly under a tap. NEVER use detergents or any other cleaning agents. Once flushed, switch off the water again and follow steps 1-2 to open the filter housing and reinstall the cartridge. Refit the top of the filter body and switch on the water supply, remembering to check for leaks.
To Replace the Cartridge
- Insert the new filter block into the body. Refit the top of the filter body and switch on the water supply, remembering to check for leaks.
- Flush the new filter according to the manufacturer’s instructions, usually for 5-10 minutes.
Our comprehensive guide should have taken some of the confusion out of your decision as to whether an under sink water filter is right for you and given you some guidance on the best model for your needs and your budget.
For homes served by municipal water supplies, under sink water filtration systems are an effective, affordable and reliable way to improve the quality of water in your home, without having to make wholesale changes to the plumbing systems or laying out large sums of money for whole house filtration.