Aquasana AQ-4000 Review

Written by: James Smith

Updated: March 16, 2023

On the hunt for a countertop water filter? The Aquasana AQ-4000 is one of the market leaders. Find out if it’s as effective as it is popular in our review.

Aquasana aq-4000 review post

We all know about the importance of drinking water, and the difference it can make to our health. However, if you’re choosing water over a cup of coffee, you’ll want to make sure you’re getting what you expect.

Tap water is convenient and free and should be the obvious choice. Unfortunately, it’s not always as pure as you might expect. In the US, we don’t have to sterilize our water before drinking it or using it on salads so it’s easy to assume that there aren’t any problems with what comes out of the faucet.

While it’s true that you’re unlikely to be instantly struck down with a case of diarrhea – sorry, too much information there! – simply for swigging the water that comes out of the faucet, you could still end up suffering adverse effects.

Recent research suggests there could be as many as 300+ pollutants in our tap water in the US. The Environmental Working Group have a handy online tool which allows you to check which chemical cocktail you’re cheerfully chugging back but the short answer is that none of us are enjoying the healthy water we expect.

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Some of the chemicals found in tap water include fluoride, heavy metals and volatile organic chemicals such as herbicides and pesticides. If you are careful about what you eat and try to avoid any unnecessary chemicals, the truth is that you could still be absorbing them through your water instead.

Many of these chemicals enter the water accidentally such as through agricultural run-off where they pollute municipal reserves. Hormones and other pharmaceuticals are a big problem too, circulating around the water supply undetected. The biggest problem is that you can’t remove these by simply boiling your water.

However, not all chemicals enter the water supply accidentally as in many areas, fluoride is added deliberately. This is an extremely controversial subject and one that’s sparked a huge debate. Fluoride is the thing you see in toothpaste, so surely that’s isn’t harmful, right?

Unfortunately, that’s not the case. Not only is there no evidence that fluoride is beneficial to oral health when drunk, but there are also increasing concerns about the links to disorders such as thyroid problems. Don’t worry, you can still carry on using your toothpaste though!

If you’re now staring at your faucet in horror and about to sign up to a lifelong supply of bottled water, just hold your horses. Bottled water isn’t great either. In many cases, the content is exactly the same as your tap water, with the same chemicals and pollutants. It also has the added problem of chemicals leaching into the water from the plastic bottle itself. If that wasn’t enough, do we need to say anything about the environmental damage being caused by plastic?

Before you despair and turn back to the coffee, there is a way to enjoy clean, pure water that benefits your health and leaves you feeling hydrated and brimming with vitality: a water filter.

A countertop water filter is easy to use and won’t make having a drink of water complicated. You can still enjoy the convenience of tap water, but without the chemicals and with a beautifully clean, fresh taste.

Given the problems with the tap water in the US, it’s not surprising that there are so many water filters on the market. We’ve taken a look at one of the best, the Aquasana AQ-4000 – here’s what we think.

Our Aquasana Water Filter Review

Aquasana countertop water filter

Aquasana has built a reputation for being the number one provider of water filters in the US. With the AQ-4000 Aquasana have created a counter-top design that’s simple to use and easy to install.

Counter-top filters are intended to be user-friendly, but is that the case here? Have Aquasana fulfilled the promise of easy, clean water on your counter-top?


One of the biggest deterrents with under-counter filters is the difficulty with installation and the hassle it can cause. Counter-top filters have been deliberately designed to side-step all of this with a plug-in process that even your grandparents could follow.

With this Aquasana countertop water filter, it really is a case of just attaching the filter and getting ready to pour. You don’t need any plumbers and you should be up and running in less than two minutes. We think it’s pretty self-explanatory but it comes with a full instruction manual that you can also view online.

The ease of installation means that the filter is portable too. If you decide to move home you can just unscrew it from the faucet and take it with you.

The only problem is that not all faucets fit the Aquasana AQ 4000. You might be able to find a faucet adaptor but if they’re not compatible you’ll have a big stumbling block. Therefore, make sure you double check your faucet fitting before splashing the cash.

Filtration Performance

Aquasana are very diligent about the filtration they use and make sure that it’s properly certified. This means you know exactly what you’re getting and that the claims they make about the purity of the water produced can be trusted.

NSF International is an organization responsible for auditing and certifying consumer products, including food and water. The AQ-4000 is tested and certified by NSF International against NSF/ANSI standards 42, 53, and 401.

This is an impressive feat which to our knowledge is unique among countertop water filters. What this certification means is that this system can be trusted do the following:

  • Reduce heavy metals in the water, including mercury and lead
  • Reduce organic chemicals including herbicides and pesticides
  • Reduce pharmaceuticals including ibuprofen and estrone
  • Almost eliminating cryptosporidium and giardia (>99.99%)

The other benefit of getting this certification is that the results are available to the public. Often water filter manufacturers make wild claims about the effectiveness of their systems but can’t back up their boasts with facts. If you’re curious about just how effective the Aqusana AQ-4000 is then you can see the test results here. However, to save you scrolling through the data, we can cut to the chase and confirm that the quantities of contaminants present in the water were reduced by 95% or more. 

Aquasana after installation

What’s Inside?

The Aquasana AQ-4000 uses a two-stage filtration system known as Claryum®, a special type of technology which beats the opposition into submission. In fact, Aquasana say that their Claryum® filtration technology gets rid of ten times more nasties than the top pitcher filter. When you consider that all you have to do is screw the AQ-4000 filter onto the faucet, we think that’s more than worth the effort.

There are four separate steps in the two-stage filter which are:

  • Activated Carbon – reduces organic chemicals, herbicides, and pesticides
  • Catalytic Carbon – removes up to 97% of chloramines and chlorine (no-one wants to drink a swimming pool!)
  • Ion-Exchange – removes mercury and lead
  • Sub-Micron Mechanical Filtration – catches chlorine-resistant cysts (such as giardia and cryptosporidium) and asbestos.

The water that is filtered will still contain the good, natural minerals so it not only tastes great but will really benefit your well-being.

aquasana filter

Check out some countertop competition in the massively popular Berkey range.

Flow Rate

As the filter will be attached to your faucet, you won’t want to have to hang around just to fill up a pan of water. While the flow rate will slow a little, we still think the rate is more than acceptable at 30 gallons of water per hour. This will provide you with more than enough for drinking and cooking without any annoying delays.

It’s worth mentioning here that unlike other filtration systems that rely on reverse osmosis, there’s no water wastage with the AQ-4000. Every drop of water that comes out of your faucet will be filtered and available to drink. By contrast, a reverse osmosis system can waste three gallons of water per purified gallon, which is less than ideal.

Any Criticisms?

While we’ve been impressed with the performance of the Aquasana AQ-4000 and the results it achieves, there are of course some negatives to consider.

Compared to pitcher filters the AQ-4000 is more expensive and there are more significant running costs too. The filter won’t need changing until you’ve used 450 gallons, but it can be considered pretty expensive when compared to its countertop competition. 

The extra expense comes with the territory with regards to high-quality certification from NSF International. You pay a bit more for the seal of approval but you can trust that the filter will do exactly what the manufacturer claims.

Recommended Reading: Check out the competition in our reviews of the APEX and New Wave Enviro countertop systems.

Would We Buy It?

We’ve learned enough about the hazards of drinking plain water straight from the faucet to be convinced of the need to invest in a filter. Aquasana has an outstanding reputation for being a manufacturer that takes its responsibilities seriously.

This Aquasana countertop water filter is ideal for households where you’re serious about filtering your water and want to enjoy the very best possible. Without the hassle of under-sink installation, it’s easy to fit and you can take it with you wherever you go. Although the cost of the filters is higher than elsewhere, the impressive certification that this comes with makes it stand out in a crowded marketplace.

As a discreet unit that’s easy for anyone to use and doesn’t restrict access to your faucet, we think the AQ-4000 Aquasana countertop water filter is an all-around winner. As far as countertop units go, this is the clear winner.

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About the Author James Smith

James is the chief water geek here at His mission is to empower the consumer and allow people to take control of their health. His passion for water health is contagious, hopefully unlike your tap water!

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