We picked the ZeroWater filter as the top choice for chlorine removal in our review of the Best Water Filter Pitchers of 2021, due to the way their bespoke five-stage cartridge adds extra power to the standard carbon filtering mechanism. Here’s our review of ZeroWater’s filter cartridge and pour-through filter products.

zero-water-products-no-background
  • Capacity: 10 cups

  • 4.4 Stars (11k + ratings)

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ZeroWater ZD-018
  • Capacity: 23 cups

  • 4.3 Stars (10k + ratings)

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ZeroWater Ready-Pour Glass Dispenser
  • Capacity: 40 cups

  • 4.1 Stars (2k + ratings)

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Who is ZeroWater?

ZeroWater is a relatively new water filtration company that produces a range of pour through water pitchers, all using their own, specially designed 5-stage filtration cartridge.

According to the brand, this filter design is superior to most other standard pitcher or faucet filters available, which generally use just two stages of filtration: a screen for sediment, and activated carbon that filters out dissolved organic compounds. To these stages, ZeroWater filters add extra membrane screens and an ion exchange resin, which absorbs hard minerals like calcium and magnesium.

It seems that the extra effort ZeroWater puts into their cartridge design is worth it. After testing against competitors, ZeroWater’s filter was the only one to completely remove Total Dissolved Solids (TDS) from filtered water. Here, however, that a TDS count includes all dissolved elements in water, even the minerals that most consider beneficial to health.

ZeroWater filter

Source: ZeroWater

To demonstrate confidence in their product, ZeroWater have made the unusual choice of including a free TDS meter with each of their water filter pitchers, allowing consumers to test their pre- and post-filtered water for TDS in parts per million (ppm).

Like all the water filter products we review, ZeroWater products are validated by internal quality control testing to ensure build quality, as well as independent certification for filtering accuracy and effectiveness by internationally trusted bodies such as the NSF.

What are Total Dissolved Solids?

Total dissolved solids (TDS) refer to all that solid matter that’s dissolved in water, whether that means beneficial salts and minerals, organic stuff from the earth, or unwanted pollutants and contaminants. Usually, TDS are made from a mix of calcium, magnesium, and sodium, depending on the composition of the bedrock in the area where the water was sourced.

While it’s often a matter of personal opinion whether to filter out mineral salts, other TDS should always be removed if possible. These include volatile organic chemicals (VOCs) and nitrates, which can enter the water supply in groundwater areas where there are high levels of farming and agriculture.

ZeroWater: Key points

What to look for in a Reverse Osmosis Water Filter

Contaminants removed

Contaminants Certification to remove Products
Harmful contaminants: Lead, Asbestos, Arsenic, Mercury, Cysts, VOCs etc.* NSF 53, 58 Aquasana OptimH2O, APEC RO-PH90, GE RO System, Whirlpool RO System, Brondell Circle RC100
Chlorine and Chloramines/aesthetics issues NSF 42 Aquasana OptimH2O, Whirlpool RO System, Brondell Circle RC100
PFAs P473 Aquasana OptimH2O
Emerging contaminants NSF 401 Aquasana OptimH2O

*Check with product performance data sheets if you are concerned about a particular contaminant.

The top factor in choosing a RO water filtration system is the number of contaminants removed, or how much of a specific contaminant a filter can remove.

If you are worried about the quality of your water and are unsure of what is in it, then you should aim for the best product available that eliminates the most contaminants possible

If you know exactly what contaminants are in your local water source, you can be more precise in your purchase. For example, if your local water source has trace amounts of lead in it, then you will want a water filter that can filter over 99% of lead, and other contaminants may not be as much of a worry for you. 

RO water filters commonly remove the following contaminants: chlorine, iron, lead, asbestos, TDS (total dissolved solids), bacteria, cysts, and fluoride along with many others

We recommend finding out what contaminants are in your water source by checking your local Consumer Confidence Reports (CCR), or getting your private well water tested. This is because different systems remove different contaminants so choosing your product should be based on your specific needs. 

Here are our main contaminants of concern and reasons why:

There are also many other contaminants (too many to list), but if you get an RO water filter you can do your best to protect yourself and your loved ones from any adverse health effects. 

Because of the potential for lead to get into your water through leaching from old pipes after it leaves the water treatment facility, we do not recommend any RO products that have not been certified or tested to reduce lead.

Certifications

To be sure filter systems are filtering out what they claim to, look for products that have NSF (National Sanitation Foundation) or WQA (Water Quality Association) certifications that are the gold standards in the USA for water filtration systems. NSF and WQA marks are meant to provide proof that a product was “impartially reviewed to established standards or guidelines,” states the NSF.org website.

NSF and WQA marks also confirm that product labels and their claims have been objectively verified by a trusted third party and demonstrate a company (or organization’s) commitment to quality, compliance, and safety. The mark, which is recognized in more than 180 countries around the world, has varying associated numbers that range from the automotive industry, retail products, lab equipment, nutritional products, sustainability, and of course, water, wastewater, and food safety. 

For Reverse Osmosis filters, look for the following certifications:

  • NSF 42: Is certification to reduce mainly aesthetic or non-health related issues. These include chlorine, taste and odor, iron, manganese, and zinc.

  • NSF 53 and/or NSF 58 – Are certifications to reduce or eliminate contaminants that have known negative health effects. NSF 53 products have a carbon filter and can reduce contaminants to various degrees depending on the quality of the filter. 

    These contaminants include heavy metals (e.g., lead), Cryptosporidium, Giardia, pesticides, herbicides, benzene, MTBE, radon, trihalomethane, and PCBs. NSF 58 refers to reverse osmosis (RO) membrane filters, which can remove perchlorate, fluoride, nitrate, nitrite, radium, bacteria, cysts, and heavy metals. It is important to note that carbon filters and RO systems have many crossovers, but they do not filter out all of the same contaminants, as such they can be used in conjunction with one another in the same system.

  • NSF 401 – This certification is for new and emerging compounds, mainly as a result of pharmaceuticals, herbicides, pesticides, chemicals, flame retardants, and detergents being found in tap water that were previously not present.

  • NSF P473 – Certification to reduce PFAS, including PFOS (perfluorooctane sulfonate) and PFOA (perfluorooctanoate). To make this claim the product must be below to EPA healthy advisory limit of 70 parts per trillion.

Look for multiple certifications when searching for a water filter, and make sure they line up with the contaminants you either know or suspect are in your water source.

Best overall

NSF: 42, 53, 58, 401, P473
Price: $208.99

After getting through our top factors in choosing a reverse osmosis system, which are contaminant removal and certifications to prove it removes contaminants we wanted to introduce you to our top-rated product. It ticks a lot of our boxes, and to be our top choice it had to.

OptimH2O Reverse Osmosis Claryum Under-Counter Water Filtration System with Chrome Finish Faucet

Pros:

  • Removes 99% of harmful contaminants including arsenic, lead, PFAS, and bacteria

  • Certified to NSF 42, 53, 58, 401 + P473

  • Compatible with well water systems

  • Large filtering capacity

  • RO + Carbon + Claryum + Remineralization

  • Value

  • 2 year warranty

Cons:

  • Slower flow rate than some RO models

Buy from Home Depot

The Aquasana OptimoH2O has impeccable filtering, here are some of the main contaminants it can reduce or remove:

  • Lead: 96.6%
  • Chlorine: 97.66%
  • Arsenic: 97.6%
  • Cysts: >99.99%
  • Emerging compounds: >94.2%
  • PFAS: 96%
  • Asbestos: 99%

Performance data sheet

Being tested and certified by the NSF to NSF/ANSI standards 42, 53, 58, 401 + P473, it is one of the most comprehensively certified RO systems available. 

The Aquasana OptimoH20 utilizes a reverse osmosis membrane to reduce 14 impurities, and a patented Claryum filtration method to reduce 60 other contaminants. The filtering process is finished by remineralizing the filtered water with healthy amounts of calcium, magnesium, and potassium, which provides alkaline, pH balanced water. Here is a breakdown of the 3 stages + remineralization:

  1. Carbon filtration: Reduces organic chemicals, VOCs and MTBE
  2. RO membrane filtration: Filters out dissolved solids smaller than 1 micron including heavy metals.
  3. Claryum filtration: Targets chlorine and chloramine (aesthetic issues)
  4. Remineralization: Healthy amounts of minerals are absorbed back into the purified water to raise the pH level to a balanced level.

The Aquasana OptimoH20 is also our best RO system water filter for well water. With over 13 million American households relying on well water for drinking, it’s important to keep the water you drink from your well clean. Well water can have microorganisms such as bacteria, viruses and parasites in it, as well as nitrates, heavy metals, organic chemicals, radionuclides, and fluoride. 

Essentially anything that can contaminate water can be in a well water source depending on where you live. The Aquasana filters 99% of bacteria, putting it in the top 1% of RO systems we assessed.

The filter life for the Aquasana Optimo is solid with the Carbon and Clayrum filters needing to be replaced every 6 months or 365 gallons, which will cost you ~$65. The RO membrane needs to be changed every 1-2 years according to Aquasana and will cost ~$60, and the remineralizer costs ~$30 and needs changing once a year. If you use less water in your home than you’ll only need to replace the RO membrane once every 2-3 years.

The total system and running cost (filter replacements) for 5 years will cost approximately ~$815, which is an amazing deal considering you are getting the best RO water filter on the market.

The system can give you up to 32 gallons per day, men require about a gallon of water a day, and women require just under 3/4 of a gallon a day according to the Mayo Clinic. So if you take this into account, it can provide enough drinking water for a large family.

Reverse osmosis systems require adequate water pressure to be able to function effectively. Before purchasing, you’re going to want to make sure you have at least 40 psi in your home.

If your home’s water pressure is below 40 psi, you’ll want to look for a RO model that has a booster pump. If your home uses well water, you’ll need to make sure the well pressure of the tank is set high enough to let the RO system work best.

Filter capacity depends on how much water you and yours are going to be using. Are you using it for drinking, washing, ice trays, or a combination of all three? Different systems filter different amounts so you’ll need to adapt accordingly. 

If you are just looking for an RO system to fulfill your drinking water needs, then get a system that gives at least 9 gpd

If you want to soak some dishes as well, then systems over 10 gpd will be better. And if you are a large family that will be using an abundance of filtered water, then a system that can filter over 30 gpd may be best

Some models promote being able to filter 400 gpd, but this is unnecessary, no one will use that much water in a day, and if you do, you’re likely being very environmentally irresponsible.

An unfortunate downside to RO systems is that they can create a lot of wastewater

Ideally you’ll want to look for systems with 1:1 to 3:1 ratios if wastewater is something you’re concerned with. Consumers can also find systems designed to reduce waste by repurposing it towards other hydro uses like gardening or dishwashing. 

Systems with 1:1 ratios that are certified are difficult to find, and often they do not make their performance data readily available. 

With reverse osmosis systems, the drain ratio average is 3:1. High ratios hover around 5:1, but to reduce many contaminants these systems usually need excess water to drain out contaminants.

We suggest you look for a model around the average 3:1 ratio, but don’t rule out higher ratio models, especially if you can repurpose excess water. We suggest using it for watering gardens.

Most RO systems require installation meaning a dedicated faucet and drain connection. If you’re a renter and can’t install a faucet or alter the already built-in plumbing, you’ll want to consider a countertop model, pitcher, or other filtration method. 

If you’re a homeowner and you’re willing to do minor alterations, the RO system will be a great and long-lasting filtration option. 

People with a ‘can do’ attitude and minor DIY skills will be adept at installing RO systems in a matter of minutes by following easy-to-follow instructions that come with every product. Some of which even offer instructional videos.

RO systems are designed to strip the water of not only its harmful contaminants, but also valuable minerals. The process makes the water slightly acidic, to restore pH levels some models offer remineralization

The remineralization feature inserts healthy and valuable minerals back into the water at the end of the filtration process. If you’re looking for healthy minerals in your water, consider models that offer remineralization.

RO systems have a wide-range of pricing with low-end products at $100 and “premium models”at $1,000. Marketing teams will try and lead you to believe that more expensive units offer more filtration stages that can filter more water at a time. This is however not always correct. 

We’ve found the best products or usually in that mid-range price category. Mid-range products will get the job done, and you won’t be spending needless $.  We recommend spending around $200-300 for the purchase of a reverse osmosis system. 

In addition, you’ll also want to take into consideration the annual cost of having a filter system, like individual filter replacements. You’ll likely save money on all the bottled water you won’t be buying anymore.

RO systems usually have multiple filters with different lifespans so it might be beneficial to protect your investment with a warranty

Some products offer multiple-year warranties and we’d recommend buying products with at least a one-year warranty. 

So, with all that said, here are some more of our best reverse osmosis systems to consider going forward. We tried to give you a range of specifics to help cover as much ground as possible.  

What makes under sink water filters different?

Truly on-demand

Thanks to the way they combine with your sink, these filters are sleek and highly versatile. A dedicated filter faucet makes it easy to fill glasses or pots for cooking with one hand.

Unlike pitcher filters, most models don’t use a reservoir—meaning there’s no annoying wait for water to feed through the system, RO systems can be an exception, but their holding tanks should be large enough that you never have to wait for water.

A step up in filtering power

Some under sink filters at lower price points use the same filtering mechanism as other kitchen designs. But the majority employ larger, more powerful filtration methods, harnessing mains pressure to push tap water through dense carbon blocks or reverse osmosis membranes (see below).

This leaves tap water purer, better tasting, and potentially safer than when using a pitcher or faucet-mounted solution.

Style considerations

Most under-sink models either send water directly through your pre-existing faucet or through a secondary tap, mounted around your sink. Here, many under-sink filters are supplied with their own water dispensers—but you don’t necessarily need to use the dispenser that comes out of the box. Sourcing your own faucet for an under-sink filter can add to the look of your kitchen, making the filter seem more integrated with your other appliances.

The ZP-010 is ZeroWater’s classic pitcher-style product, and we think it’s a great alternative option to mainstays such as the Brita filter. Its price is highly competitive, it looks great, and its 10-cup capacity means that couples and small families should be able to use it without becoming frustrated by the constant need for refills.

  • Removes common contaminants:
    Lead, Mercury, Chromium, Chlorine

  • Filter mechanism:
    Carbon + Ion Exchange

  • NSF Certifications:
    42, 53

  • Capacity:
    10 cups

  • Customer rating:
    4.4 (11,583 ratings)

Check the latest price

Contaminant-wise, we gave the ZP-010 our pick for Best Water Filter Pitcher for Chlorine (in terms of taste and odor). But the filter can do a lot more than reduce or remove organic chemicals such as chlorine and others used by public treatment works. All ZeroWater filters using this 5-stage filter are certified by the NSF to remove both lead and chromium, which is unusual for handheld pitcher filters. Specifically, this product is listed as removing:

  • Chlorine, at >97.5%
  • Lead, at >95.9%
  • Chromium, at 99.56%
  • Mercury, at 96.7%

At this level of filtering power, users can feel confident that the ZP-010 will improve the taste and odor, as well as the safety, of any standard mains water supply (pitcher-style filters should never be used to sanitize untreated water). It is worth pointing out, however, that some drinkers will consider ZeroWater filters overkill, and may find the taste of filtered water—without the mineral salts removed—to be odd or tasteless.

The ZeroWater ZP-010 includes a TDS detector pen, a comfort grip handle, push-to-dispense spigot, making it much easier to fill large containers without needing both hands.

Here’s the Performance datasheet for the ZeroWater ZP-010, which breaks down the exact details of its filtering capability.

The ZD-018 uses the same filter cartridge as ZeroWater’s pitcher product, with a different water container.

ZeroWater ZD-018
  • Removes common contaminants:
    Lead, Mercury, Chromium, Chlorine
  • Filter mechanism:
    Carbon + Ion Exchange
  • NSF Certifications:
    42, 53

  • Capacity:
    23 cups

  • Customer rating:
    4.3 (10,118 ratings)
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This filter more than doubles the capacity, and 23 cups, while still remaining streamlined enough to fit into most refrigerators (with a bit of careful reorganizing). The full size of the ZD-018 is 14.96 x 5.51 x 10.63 inches.

Just the previous filter, a TDS detector pen is included, as well as a spigot tap, which arguably makes more sense in this static model than in their portable pitcher. Here, simply open your fridge door and press the button for chilled, purified water—we think this is no less convenient than most built-in fridge filters.

ZeroWater’s Ready-Pour Glass Dispenser won’t fit inside your fridge, but it will look stylish on your countertop. With a huge 40 glass capacity, this model will last for a day or more, and while it doesn’t produce chilled water, it contains the same effective 5-stage filter, which cleans water of all Total Dissolved Solids.

ZeroWater Ready-Pour Glass Dispenser
  • Removes common contaminants:
    Lead, Mercury, Chromium, Chlorine

  • Filter mechanism:
    Carbon + Ion Exchange
  • NSF Certifications:
    42, 53

  • Capacity:
    40 cups

  • Customer rating:
    4.1 (2,157 ratings)

Check the latest price

ZeroWater 5-stage filter

One of the main selling points of ZeroWater’s product line is their 5-stage filter, which combines carbon filtering with an ion exchange resin to further reduce contaminants.

The majority of reviews about this filter are highly positive, with those living in areas with highly contaminated water noticing big differences in the taste of their supply. However, many of those same reviews also warned about the lifespan of the filter when used on heavily polluted water. One review commented that “they need to replace the filter every three weeks! Which is more expensive than just buying bottled water,” so this definitely something to bear in mind.

ZeroWater’s five-stage filter

What is activated carbon?

Activated carbon is porous charcoal that’s ground into a fine powder, creating millions of pores for catching contaminants.

Carbon filters are capable of binding any carbon-based (organic) contaminant, which includes chlorine and Volatile Organic Chemicals (VOCs). VOCs are by-products of industrial processes and manufacturing, as well as being found in household products such as paint and cleaning fluids.

Unless they are structured in a particular way, carbon filters won’t significantly reduce bacteria, viruses, or most metals.

What is ion exchange?

Ion exchange is the most common method for reducing water hardness, which refers to the level of mineral salts dissolved in water—especially calcium and magnesium.

ZeroWater 5-stage filter

Since 1944, the National Sanitation Foundation (NSF) has been certifying water filter products in their independent labs, setting product standards that are acknowledged by the International Organization for Standardization (ISO) and the American National Standards Institute (ANSI).

When it comes to the home filters used in kitchens across the country to purify water that’s already been treated, there are two NSF certifications that are most relevant:

  • Standard 42, which covers the safety of filter materials and claims related to the taste and smell of water.
  • Standard 53, which covers any health-related claims made by filter manufacturers, such as the ability to reduce or remove lead, volatile organic chemicals (VOCs), or bacterial contaminants.

When it comes to NSF certifications, it’s important to remember the standards only apply to claims made by manufacturers. In fact, the presence of an NSF mark rarely means that everything in that category is removed by a filter.

Here’s our explainer on Water Filter Certification, for the full details on what each marker of confidence means.

Our verdict

ZeroWater’s filters are great value-for-money and come in a variety of shapes and sizes, meaning that they offer a solution that works for most families. All of these products use the same 5-stage filter, which takes the purification of pre-treated water a step further than most filter brands, using ion-exchange resin to remove most or all Total Dissolved Solids.

If you’re looking for a filter that will purify your pre-treated tap water to this extent, then ZeroWater should be top of your list. However, we don’t think that most customers actually want, or need, to drink water that’s free of some TDS, such as mineral salts.

Also worth bearing in mind are customer reviews, which seem to suggest that those living in areas with highly contaminated water experience much shorter filter lifespans. This isn’t great to hear, considering that it’s these people who rely on water filters the most.

Check out the latest price of ZeroWater filters now.

Disclaimer

At CleanCoolWater, we endeavor to provide the most accurate, honest water filter reviews on the internet. We base our product recommendations on the best available public information, spending hours analyzing data on product quality and safety. However, we can’t guarantee that product specifications will always match our descriptions, nor can we validate any claims made by manufacturers.