Aquasana AQ-4000 Review – Countertop Drinking Water Filter System

Author: Rory Mullan - Published: 2021/07/05 - Updated: 2023/01/05

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This product review features the Aquasana AQ-4000 countertop water filter.

The Aquasana AQ-4000 is one of the more popular choices for countertop water filters in the USA, thanks to a fast setup, ease of usage, and NSF certifications.

It removes up to 77 harmful contaminants, including chlorine, chloramine, herbicides, pesticides, heavy metals and VOCs, from your drinking water. Given that these contaminants can’t be removed by merely boiling water, an efficient filtration system is crucial.

Still not sure whether the Aquasana AQ-4000 a good choice for your house? Here, we outline everything related to it and whether it’s the best fit for you.

Aquasana AQ-4000 Review – Main Specs

Aquasana AQ-4000 Countertop Drinking Water Filter


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  • Filter stages: 4
  • Flow rate: 0.5 gallons of filtered water per minute
  • Estimated filter replacement cost per year: $120
  • NSF: 42, 53, 401, P473
  • System dimensions: 9″ x 4″ x 9.5″ (L x W x H)
  • Operating pressure: 20-80 psi


At the beginning of our Aquasana countertop water filter review, a few highlights:

Four-Stage Filtration

The Aquasana AQ-4000 countertop filter features four stages of filtration using two cartridges. The manufacturers claim that the unit removes fifteen times more contaminants compared to leading water filter pitchers.

Here is how it works:

  1. Activated carbon: The first filter stage removes harmful chemicals like chlorine, pesticides, VOCs, and disinfection byproducts.
  2. Catalytic carbon: Here, your water is purified from chloramines etc.
  3. Ion-exchange: The ion-exchange media targets heavy metals like lead and mercury.[1]
  4. Sub-micron mechanical filter: This highly complex filter traps particles down to the sub-micron level, including asbestos, a harmful carcinogen.

You can refer to the complete list of contaminants the system can remove.

Strong Flow

The water flow rate is fast enough to provide an entire family with drinking water.

Plug ‘n’ Play

The countertop water filter is installation-free. Hooking it to your kitchen faucet takes 2 minutes. Great for renters and portability.

77 Contaminants Removed

Four NSF certifications underpin the system’s filtration effectiveness. Reduction rates for 77 contaminants have been tested and met certification standards.

90 Days Refund

You can return the system within 90 days after purchase for a full refund.


  • Most importantly, the system can fill a glass of water in 7 seconds, thanks to a flow rate of 0.5 gallons per minute.
  • The countertop water filter is a sleek and compact unit that is entirely portable. Since it doesn’t require permanent installation or elaborate fittings, all you need is to do is – plug and play. It doesn’t get easier, does it?
  • The unit filters water on demand, and therefore there are no bulky canisters or tanks. It fits seamlessly on your countertop without taking up much space.
  • You can easily switch between filtered and unfiltered water due to the diverter valve in the unit. This feature ensures you can quickly turn off the system when not in use.
  • Did we mention that the Aquasana 4000 only removes harmful contaminants, not the good ones? Most filtration systems, especially RO filters, eliminate calcium, potassium, and magnesium from your water. With the Aquasana AQ-4000, your water is healthy as well as crystal clear.
  • One set of filters lasts up to six months or 450 gallons before needing replacement.
  • NSF certifications (42, 53, 401) and Protocol 473 back the company’s claim that the system removes 95% of the most common contaminants in your water.
  • If you have any issues with the system, you can ask for a full refund within 90 days. Convenience at its best!
  • Finally, a one-year limited warranty makes repairs hassle-free.
  • The unit is manufactured in the USA, ensuring premium quality.


  • While setting up the system is straightforward, replacing the system is rather complicated. Several users have pointed out that the filter caps are hard to remove. This means you require muscle power and time at every filter change.
  • Likewise, the Aquasana AQ 4000 is not compatible with all faucets. However, the package includes two adapters that you can use if the system doesn’t fit. Still, it’s best to consult Aquasana support to know if your faucet is a good fit for the unit.
  • At the same time, we have also read about leakages in the unit. There have been instances where the system leaked completely, or water began trickling from the diverter valve or hoses. You need to remove the unit, or else your countertop will be flooded in no time. Thankfully, you can ask the manufacturer for a replacement free of charge.
  • Finally, the diverter valve appears to be of low quality. This is evident by numerous complaints of the valve getting rusty and stuck. However, an occasional oil spray keeps the valve greased.


Setting up the system is a quick and straightforward process that anyone can manage. As a matter of fact, there are no lengthy steps since the system is highly portable (link to the manual).

  1. Begin by removing the aerator from your faucet and attach the diverter.
  2. You might need to use the brass adapter to fix the diverter. Tightly screw it in place using the plastic hex wrench.
  3. Next, take the tubing and attach them to the button of the unit. Push the blue pin in the blue cap and the white tip in the white cap.
  4. Set the system on the counter and turn on the tap to check for leakage.
  5. Now pull the diverter pin out and let the system flush for ten minutes.
  6. Congratulations, you can now enjoy filtered water right out of your tap in a matter of seconds.

Refer to this online video to make things easier.


The two filter cartridges last for 450 gallons or around six months.

We assumed that the compact filter couldn’t be much of a handful when it comes to filtration, but that’s quite the exaggeration.

The process seems simple but gets complicated since the caps get stuck when not moved for six months. Sometimes, users had to order a new system because they couldn’t replace the filters.

Try this quick fix that might work for you: Remove the blue filter, and use the corner to twist the corner of the white filter. When putting the filters back, place them both in opposite directions.

What’s Included

Here are the contents of the package.

  • Filter system with filter caps
  • Filters
  • Diverter valve and hose assembly
  • Faucet adapters
  • Washers
  • O-rings
  • Hex wrench
  • 2x brass faucet adapters

Aquasana Countertop Water Filter Review – Conclusion & Best For

The Aquasana AQ-4000 countertop water filtration system is best if you love making things easy. Seamless set-up, advanced filtration, sleek design and bi-annual filter changes make the system our top choice.

Yes, it’s not highly durable, and leakage issues have also been observed. With this in mind, we suggest changing your filters on time and handling the unit carefully. At the end of the day, it’s fast and does the job well.

If you have questions about our Aquasana AQ-4000 review please leave a comment below!

Further Reading


Meet Rory Mullan

Rory Mullan Rory has joined the Water Masterz team as a contributing writer. He has covered all sorts of topics in the last several years.

Outside of his writing work, Rory enjoys photographing the Irish landscape and making music!

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