Best Under Sink Water Filter

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Let’s face it: water safety is not as reliable as it was just a few years ago. Old pipelines are but one potential reason why we might be pouring toxic chemicals and harmful organisms into our bodies every time we help ourselves to a glass of water. Leaving it to chance is a luxury we might no longer have. Here we will be covering why an under sink water filter might be your best bet, how to identify the ideal fit for your particular water source, and some great options for you to consider.

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Why an Under Sink Water Filter?

5 years. That’s how long you can go, in some cases, without having to tinker with one of these filters. Given the way in which they are installed, they do not interfere with the aesthetics of your living space. They are also larger, which makes them more complex and therefore capable of removing a larger volume of impurities from your drinking water.

Finding The Best Under Sink Water Filter

There is much to consider before buying your filter: money, effort and more will vary between one option and another. Remember to measure the space available under the sink, so you may identify if a filter might be too big before buying it.

Installation & Filtering Method

Depending on how they get the job done, filters will be installed differently. Here’s a breakdown:

1. Conventional

This one latches on to the cold water line, letting the filtered water through and pouring it out of a separate faucet. You can pour unfiltered water, either cold or hot, out of your original faucet. This arrangement helps your filter last longer, as the flow of water is less constant. However, the need for an additional faucet makes installation a little bit more complicated —you might even have to drill a new hole on your countertop, to make room for the extra faucet.

2. Simple

No additional faucet and no drilling needed: every drop of water that goes through the cold water line passes through the filter, streaming out of the usual faucet. This sort of filter will be working much more frequently (every time you use the sink), so you will have to change it more often; but installing it is so easy, you don’t even need a professional to do it; and you can take it with you if you move!

3. Reverse Osmosis

A Reverse Osmosis system uses “a process that reverses the flow of water in a natural process of osmosis so that water passes from a more concentrated solution to a more dilute solution through a semi-permeable membrane” (CDC). A filter of this type will have pores as small as a fraction of a micron (for context, an average human hair is about 50 microns thick). This process is extremely effective at eliminating a wide variety of microorganisms, and is capable of removing or reducing several types of chemical toxins.

The biggest drawback with an RO filter is the cost in money, time and effort. More likely than not, you will need an experienced plumber to get it working, in addition to its higher price tag.

What Is Removed

RO filters can take pretty much anything harmful from your drinking water. Simpler filters might only be good for removing chlorine. Knowing what it is you want filtered out is important: that way you can get the right unit for the job.

Under The Sink Water Filter Certifications

It always helps when a neutral, dedicated party vouches for a product, especially when it’s our health on the line. Filters can come certified by a variety of organizations, such as the International Association of Plumbing and Mechanical Officials (IAPMO) or the Illinois-based Water Quality Association (WQA).

Water Pressure

Pretty much any water filter in this category will need to rely on stable water pressure to get the job done. To get the desired results, it is important to know if the house meets the level of pressure required by a given filter. A gauge should prove supremely helpful in finding this out, but you can also get an approximate measure if you have a bucket with a capacity of exactly 1 gallon. Just follow these steps:

1. Shut off all water faucets, spigots and even appliances that consume water, such as the dishwasher and the laundry machine.

2. Bring the 1-gallon bucket to a water source in the basement or bottom floor. These are the closest to the main supply and this helps minimize loss of pressure for more accurate readings.

3. Time how long it takes for the bucket to fill up completely. Write down the result.

4. Divide 60 by the number of seconds it took for the bucket to fill up. This gives you the gallons per minute. For example, if the bucket took 20 seconds to fill up, then you divide 60/20, for a result of 3 gpm.

Ratio Of Water Wasted

Particularly relevant if you choose to go the RO route. Older systems could waste as many as 5 gallons of water per gallon they purified, which will definitely show in your water bill. Newer systems are better at it, sometimes going as low as 3 gallons of water wasted per gallon they clean.

Duration Of Filter

The longer you can wait in between replacements, the better, as going under the sink to replace a filter can be quite uncomfortable. You might find filters that need swapping only about twice a year without too much effort.

If you choose reverse osmosis, see that the membrane comes with a few pre-filters. These might need changing every few months, but this way you might not need to concern yourself with a new membrane for a while, perhaps even years.


In the process of pulling as much harmful matter as possible, your drinking water might become too acid and therefore bitter. Some filters will apply a given amount of minerals after filtration to restore pH balance and give your water a sweeter, more pleasant taste.

Water pressure. Under sink space measurements. Contaminants that we want removed. With these details in hand, it’s time to check out some good options for improving your water quality.

The Filter Roster

iSpring RCC7AK – RO

iSpring RCC7AK-RO water filter for under the sink

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This is such a complete package, even installation might be good for DIY: the kit comes with everything you need to hook it up, including detailed instructions. The RO filter features pores 0.0001 microns in size, which, coupled with its 3 pre-filters, enable it to remove hundreds of chemical toxins, including asbestos, arsenic, lead, chlorine and more.

Because it is so thorough, even beneficial minerals are filtered out, which is why the 6 and last stage of the filtering process involves remineralization to restore the water’s optimal pH. Filtered water to wasted water ratio is 1:3.


  • Very low waste ratio.
  • Thorough process that includes remineralization.
  • It can be installed without having to call a professional.


  • Housing can be somewhat fragile, leading to leaks.

Frizzlife 8541998827

Fizzlife under the sink water filter

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Installing this one is pretty straightforward; you don’t need any tools, let alone a professional. Hook it up to your cold water line and forget about it for a few months. Purifying process is two-stage, running the water through pores half a micron in size. Contaminants removed include chlorine and heavy metals.

Replacing the cartridge is not done in the usual way: only the core part is replaced, with the plastic casing staying in place for as long as the filter itself will last. The built-in auto shutoff function allows to replace the cartridge without even having to cut the water flow.


  • NSF certified.
  • Removes toxins without affecting pH; water is widely regarded as having good taste.
  • Replacing cartridges is simpler and more economical.


  • It can slow water flow down to a trickle.
  • Replacement cartridges might not be in stock from time to time.

APEC Water Systems ROES-50 Essence Series

Apec water filtration system under the sink

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Your own measurements will have the final say but, at 16” x 5.2” x 17.5” size, this one might have to end up in the garage instead of under the sink. Purifying process is 5-stage, aimed at removing a wide variety of harmful chemicals, including arsenic, barium, chlorine, radium and more. The included carbon blocks are extra large, with the intention of maximizing contact with the water.

Even though the kit includes detailed instructions (printed and online) so a professional does not have to be involved, installation can be a bit problematic.


  • Reinforced fittings help prevent leaks.
  • Carbon blocks help filters last longer.


  • Water does not get remineralized.

Woder WD-10K-DC

Woder under the sink water purifier

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It might give you extra peace of mind to know that this unit has earned NSF/ANSI certifications by the WQA for removal of chlorine and lead, as well as taste and odor. Filters involve micro particles, which enhances purification and helps the filters last for as long as 3 years.

Its proprietary selective filtration process helps keep the good minerals in the water, eliminating the need for remineralization. However, it can only be used on water that has been municipal treated: it should not be hot, salty, softened, or from a well.


  • Filters last much longer than with other units of its category.
  • Lower priced.


  • Very specific water requirements to work properly.
  • Might require adapters to work with certain sinks.

Culligan US-EZ-4

Culligan water purifying spigot under the sink filter

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This one comes IAMPO certified for removal of chloramine, turbidity, chlorine taste and odor, lead mercury and more. Filter is twist-on, and changing it does not even require shutting off the water supply. An LED indicator will alert you when the filter needs replacing, roughly every 500 gallons or 6 months, depending on the water.

Kit comes with everything required for installation, including the separate faucet through which purified water will flow. The only potential step added is drilling an extra hole for the supplemental faucet.


  • Installing unit and changing filters has been remarkably simplified.


  • Might require a professional to drill an extra hole for the additional faucet.
  • Build is not very solid.

Best Under Sink Water Filter: Woder WD-10K-DC

Under the sink water filtration unit Woder

It does have fairly specific requirements for the sort of water it can work with, but those requirements are a given for almost any home, as the water is already treated by the city. Certification helps ensure that the unit will deliver what it promises. That’s only half of what goes into the best under the sink water filter.

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In terms of cost, it’s hard to beat: aside from a fairly affordable base price, its simple installation means you won’t have to get a professional involved. Filters last for a while too, further driving down your expenses. And you will not be losing minerals, which means no altered taste: you might even find yourself toasting to your health with your freshly filtered water!


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