Aquasana AQ-4000 Countertop Water Filter System Review 2023

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The Aquasana AQ-4000 is a countertop filter system that converts plain tap water into clean, great-tasting drinking water on demand.

Thereby, the unit does not require permanent installation to your plumbing system or kitchen sink whatsoever. Quite the contrary: The AQ-4000 attaches to faucets in a matter of minutes, no tools required… A solid investment?

Aquasana AQ-4000 Review

Aquasana AQ-4000

Price: $
Flow Rate: 0.5 gpm
Filter Capacity: 450 gal
NSF Certifications: 42, 53, 401, P473
Warranty: 1 Year

Our Rating

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Aquasana AQ-4000 Countertop Water Filter – Key Features

Once set up, the Claryum filter uses carbon and ion exchange media as well as sub-micron filtration to help you get rid of:

  • Chlorine and chloramines (>97%)
  • Heavy metals (lead >99.3%, mercury >95%.8)
  • Chlorine resistant cysts like giardia and cryptosporidium (>99.99%)
  • Organic chemicals including herbicides, pesticides and VOCs (between 95% and more than 99%)
  • Pharmaceuticals such as Estrone (96.5%) and Ibuprofen (95.4%)
  • PFOA and PFOS (96%)

All reduction rates are according to official test data.

Total number of contaminants removed: 77

NSF certifications: Standards 42, 53, 401 + Protocol P473

By the way, the flow rate you can expect is around .5 gallons per minute, so a bit slow. However, remember that a more thorough filtration requires either more time or higher pressure.

One filter cartridges is rated at 450 gallons or 6 months. If you do the math, you will end up paying much less per gallon that you would buying bottled water.

You just have to be careful because the Aquasana AQ-4000 is not compatible with all faucets. For example, it does not fit pullout sprayers. Most standard faucets are fine. Also, the package includes two adapters which come in handy if your faucet happens to be non-standard size.

AQ-4000 Pros

Usually when a filter system removes that many impurities it also eliminates some of the good stuff – think essential minerals. Not so with the AQ-4000. All calcium, potassium and magnesium will be preserved and contribute to your total daily mineral intake.

Another advantage is that you can easily switch between filtered and unfiltered water without having to uninstall the unit. Simply pull or push the pin on the diverted valve as needed.

This plus the compact size is also the reason why this countertop water filter is highly portable. And it doesn’t take up much space on your counter.

Did we mention that everything is covered by a 1-year limited warranty + a 90-day “PURE SATISFACTION” guarantee (full refund of the purchase price, no questions asked)?

Aquasana AQ-4000

The Aquasana AQ-4000 – learn more on


Like we said, the Aquasana AQ-4000 is really simple to set up – no permanent fixtures or installation required!

Here is what you need to do:

  1. Remove the aerator from your kitchen faucet.
  2. Make sure the rubber washer on the diverter valve sits in place.
  3. Attach the diverter valve. You may need to use one of the brass adapters (included). If so, tighten the adapter with the plastic hex wrench tool (included).
  4. Push the two hoses into the holes on the bottom of the unit (turning it upside down). The blue tip goes into the blue cap, the white tip into the white cap.
  5. Open your faucet and check for leaks.
  6. Pull out the diverter pin.
  7. Flush for 10 minutes.


Here is a short video outlining the setup process step by step:

The Package (Parts)

  • Unit with snap-on cover
  • Threaded cartridge caps
  • 2x O-rings
  • 2x filter cartridges
  • Faucet diverter valve and hose assembly
  • 2x brass faucet adapters, different sizes (13/16″ and 15/16″ male)
  • Rubber washers
  • Plastic hex wrench


In theory, filter replacements couldn’t be more straightforward. All you really have to do is put the unit on its side, twist off the filter caps, take out the old cartridges and insert new ones – shouldn’t take more than 2 minutes, right?

Yeah, not quite. The caps get easily stuck making the whole process a nightmare. Some users would even order a whole new unit because they couldn’t manage to open their old one.

A possible solution to this is to remove the blue filter first. Then use the fins on its end to twist the fins of the white filter. And make sure to not install both in the same direction. The white goes in nipple-first, the blue one the other way round.

At least you only have to do this about every 6 months…


If you are looking for a manual follow this link:

AQ-4000 Cons

Filter replacements are by far the biggest issue. After 6 months of use the filter caps are likely stuck having caused multiple incidences of bloody knuckles.

The next problem is leaking. Either water will pour out the bottom of the unit or out of one of the hoses or the diverter. If the pin is leaking, it’ll spray water all over the place. The good news is that the manufacturer is usually willing to send replacement parts free of charge.

And lastly, the diverter. It might get stuck due to corrosion or keeps popping out so that you can’t switch between pure and plain tap water anymore. A simple tip we read in one of the customer ratings is to grease the pin with vegetable oil.

Aquasana AQ-4000 Review: Our Verdict + Best for

Bottom line: The Aquasana AQ-4000 provides pure water with great taste. Although there have been issues, for the vast majority of people the countertop system has done a great job as long as filters are changed on schedule.

The price is affordable. And considering the 90-day money-back guarantee, what can really go wrong? Our verdict: 4.0 stars!

The Aquasana AQ-4000 is best for people looking for an affordable yet effective countertop filter that’s NSF-certified for removing a wide range of contaminants from drinking water.

Get Up to 50% Off! Use Code: AQBOS50

More Reviews:

This completes our Aquasana AQ-4000 review. If you have any questions, please don’t hesitate to leave a comment below!

About the Author Gene Fitzgerald

Gene Fitzgerald is one of the founders of BOS and currently head of content creation. She has 8+ years of experience as a water treatment specialist under her belt making her our senior scientist. Outside of BOS, Gene loves reading books on philosophy & social issues, making music, and hiking.
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