NU Aqua Efficiency Series Review (Data-Driven Analysis)

We installed the NU Aqua Efficiency Series, a tankless under-sink reverse osmosis system, and tested a range of factors that impact its performance, ease of use, and value. This included lab-testing our water quality before and after purification to evaluate contaminant removal, and assessing filtration rate, setup and maintenance requirements, and design quality. This combined data helped us determine the NU Aqua reverse osmosis system’s overall quality and value for money.

Overall Score: 8.32

How We Test & Score

7.89 Contaminant Reduction

8.10 Design

10.00 Maintenance

10.00 Filtration Rate

7.00 Setup

9.50 Company

What We Like

Alkaline filter & UV upgrade for additional protection

Fast purification rate

Effectively remineralized our water

Superb customer service experience

What We Don’t Like

Fluoride detection was unaltered post-filtration

Not certified to reduce/remove contaminants

Issue with faulty UV purifier in initial test

Price	$469.95
Contaminants Reduced	10+
Certifications	Not Certified
Process	GAC + RO + UV
Filter Capacity	550 / 1,100 / 3,200 gal.
Annual Cost	~$200
Warranty	3 years

View at nuaquasystems.com

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📊 Scoring Data

At Water Filter Guru, every water filter we test is put through a series of 6 subjective and objective assessments within our own scoring system. We then take the results of these tests and compare them to every water filter (within the product category) we’ve tested to date. This helps us understand how a system performs next to its close competitors. 

Check out the full performance table below to see how this under-sink RO system ranks:

Criteria	Results
Overall Score	8.32
Health Related Contaminants	8.00
Aesthetic Related Contaminants	9.90
Performance Certification	Not Certified
Filtration Rate	600 or 800 GPD
Component Quality	Outstanding
Component Certification	Not Certified
Setup	Weak
Servicing Requirements	Exceptional
Costs	$0.15/ gallon
Warranty Length	3 years
Shipping	Free shipping on orders over $40 within the contiguous 48 US states
Returns	120 days guarantee, with stipulations

🚰 Contaminant Reduction

Score: 7.89

We have particularly high expectations for reverse osmosis systems, like the NU Aqua, when we’re testing them for contaminant reduction. RO is a purification method, which means, rather than just targeting a few problem contaminants, it addresses virtually all impurities present in the water.

We lab-tested our water before and after purification using SimpleLab Tap Score testing. Our results were delivered in two interactive lab reports, which we compared side-by-side to evaluate the NU Aqua unit’s performance.

The contaminant reduction score is also influenced by the presence (or lack of) performance certifications. RO systems receive a higher score if they’ve been officially certified to NSF performance standards. 

Our Performance Testing

Score: 8.10

Our performance testing score was determined by our analysis of the two Tap Score water quality reports. These documented all individual contaminants detected in our water and how they compared to the EPA and Tap Score water quality standards. 

A couple of things to note about our initial water quality and testing process:

• The system was installed in a home on treated well water. There were several pretreatment systems installed at the home’s point of entry: a 100-micron spin-down sand separator filter, a 5-micron sediment filter, a cation exchange water softener,  and a UV disinfection system.
• The NU Aqua was installed under the homeowner’s kitchen sink. We took a sample of unfiltered water first from the regular faucet, then a sample of purified water from the dedicated RO faucet. 

Health-Related Contaminants

Score: 8.00

3 contaminants exceeding the HGL were detected in our unfiltered water: 

• 0.0001889 PPM of arsenic (exceeding the HGL of 0 PPM) 
• 0.0004182 PPM of lead (exceeding the HGL of 0 PPM)
• 0.0001294 PPM of uranium (exceeding the HGL of 0 PPM)

Lead, uranium, and arsenic are all linked to human health effects, ranging from cardiovascular and developmental effects to immune and nervous system damage, respiratory issues, and gastrointestinal outcomes. 

Post-filtration, 100% of lead and uranium had been reduced, while arsenic had been reduced by 71%, to 0.000054 PPM.

Several health-related contaminants not exceeding the HGL were also detected in the unfiltered water, including copper, molybdenum, nitrate, phosphorus, iron, selenium, boron, and fluoride. 

Between 77% and 100% of these contaminants were reduced post-filtration, except for fluoride, which remained the same (0.004 PPM) post-filtration. We discuss why we think this may be under “unusual outcomes” later in this section. 

The table below lists all the health-related contaminants and their detections before and after purification in the NU Aqua. 

Property	Type	Measurement	Pre-Filtration	Post-Filtration	% Reduction
Antimony	Metals	PPM	0	0.0006581999	N.A
Arsenic	Metals	PPM	0.0001889	0.000054	-71.41%
Barium	Metals	PPM	0	0.00218	N.A
Bicarbonate	Minerals	PPM	125.74	23.06	-81.66%
Boron	Inorganics	PPM	0.01566	0.00348	-77.78%
Calcium	Minerals	PPM	0.00319	2.04674	64061.13%
Carbonate	Minerals	PPM	0.27	0.083	-69.26%
Chloride	Inorganics	PPM	10.94	0.6919999999	-93.67%
Cobalt	Metals	PPM	0.000004	0.000004	0.00%
Copper	Metals	PPM	0.0146	0	-100.00%
Fluoride	Inorganics	PPM	0.004	0.004	0.00%
Iron	Metals	PPM	0.00476	0.00072	-84.87%
Lead	Metals	PPM	0.0000894	0	-100.00%
Magnesium	Minerals	PPM	0.002	1.7001	84905.00%
Manganese	Metals	PPM	0	0.00183	N.A
Molybdenum	Metals	PPM	0.0004124	0	-100.00%
Nickel	Metals	PPM	0	0.0005074	N.A
Nitrate (as N)	Inorganics	PPM	0.997	0	-100.00%
Phosphorus	Inorganics	PPM	0.02155	0	-100.00%
Potassium	Minerals	PPM	0.02902	0.7204199999	2382.49%
Selenium	Metals	PPM	0.0023490999	0.000406	-82.72%
Silica	Inorganics	PPM	12.81681	0.85464	-93.33%
Sodium	Minerals	PPM	53.42337	1.67733	-96.86%
Strontium	Metals	PPM	0	0.0097	N.A
Sulfate	Inorganics	PPM	17.737	0.402	-97.73%
Thallium	Metals	PPM	0	0.000019	N.A
Uranium	Metals	PPM	0.0000259999	0	-100.00%
Zinc	Metals	PPM	0.00265	0.00263	-0.75%

Coliform Bacteria

One of the biggest influencing factors for our health-related contaminants score was the presence of coliform bacteria in our purified water. 

While coliform bacteria aren’t harmful, they can indicate the presence of other harmful pathogens, increasing the risk of contracting a waterborne illness when ingested in drinking water. 

In our purified water test results, coliform bacteria was listed as “detected”. Any detection is an unwanted outcome, not to mention unexpected, for several reasons: 

1. Reverse osmosis is technically supposed to remove impurities down to bacteria size (although we don’t recommend using this method to filter untreated water); 
2. AND the system we were testing had an included UV sterilization stage, which provides an additional layer of protection against bacteria in the system.

We have a couple of hypotheses about where the bacteria came from: 

1. From shocking the homeowner’s well

Before installing the NU Aqua system, the homeowner shocked their well to address coliform bacterial contamination in the water supply. During this time, the NU Aqua was installed but not turned on (the water inlet valve where it was connected under the sink was turned off). 

Because the home’s water was initially contaminated with coliform from the well, it’s possible that the plumbing system sanitization process was unable to target bacteria that may have been inside the RO shutoff valve. So, when the RO system was put into use, it became contaminated with bacteria.

2. From the homeowner’s water bottle

Another hypothesis is that the dedicated faucet for the RO system became contaminated with bacteria when the homeowner filled their water bottle. They would stick the bottle under the faucet, with the end of the faucet sitting down inside the top of the bottle. 

It’s possible that any bacteria present in the bottle migrated into the RO faucet, influencing the bacteria score. 

Either way, this result was unexpected given that RO should, in theory, address bacteria, especially with a built-in UV light. 

However, we determined that the UV light actually wasn’t working properly due to a sensor error. We contacted the manufacturer to report this issue, and they provided a new UV light and a completely new set of filters to replace the existing ones. 

They also provided a 10-stage disinfecting procedure, which involved running bleach or hydrogen peroxide through the system, to follow before installing the new filters.

After disinfecting the system and installing the new filters, we retested just for bacteria using the local county lab testing service for well owners. This time, the test came back negative for bacteria.

Aesthetic Contaminants

Score: 9.90

Drinking water may also contain aesthetic contaminants, which affect its taste, smell, and (in some cases) appearance. In our testing, the unfiltered water had been treated with chlorine, an aesthetic disinfectant that has taste and smell effects.

Post-purification, chlorine was no longer detected, earning the NU Aqua the highest score in this category.

Minerals & Salts

We don’t award scores specifically for the presence of minerals and salts in water after RO purification. But this is still an important topic to discuss because reverse osmosis actually removes the majority of minerals from water, which can affect water quality and pH. 

The remedy to this issue is post-remineralization. The NU Aqua model that we tested contained an alkaline remineralization filter, which, according to the manufacturer, adds calcium, magnesium, sodium, potassium, zinc, and iron to the water. 

Before we get into our results, it’s important to note that the unfiltered test water contained much lower concentrations of calcium and magnesium, with higher concentrations of sodium, than “normal” tap water. Why? Because the homeowner already had a point-of-entry water softener installed, so the water coming into the RO system was already softened (a process that greatly reduces calcium and magnesium and elevates sodium).

With that in mind, we expected an increase in calcium, magnesium, potassium, pH, and hardness, and that’s exactly the outcome we got:

• Calcium increased by over 6,400%, from 0.00319 PPM to 2.04673 PPM.
• Magnesium increased by over 84,900%, from 0.002 PPM to 1.7001 PPM.
• Potassium increased by over 2,300%, from 0.02902 PPM to 0.72041 PPM.
• Total hardness increased by over 23,000%, from 0.052 PPM to 12.13 PPM.
• Interestingly, the pH of the unfiltered water was already basic at 7.6, and this only increased by 3% post-filtration, to 7.89.

The increased detections of hardness-associated minerals indicates the remineralization filter is working as expected, and explains why these increases seem so large. And yes, the homeowner wanted to initially remove these hardness minerals with a water softener, but since they have taste-enhancing effects, it’s beneficial to add them back into drinking water with a POU system.

NU Aqua Reverse Osmosis Unexpected Outcomes

We also want to touch on a few unexpected outcomes with our post-purification test results. 

First, a number of metals were detected post-filtration that weren’t present in the unfiltered sample. These included:

All of these were either detected below the reporting limit, meaning they weren’t quantifiable by the testing lab, or were detected below the HGL (some were both). These minerals are likely coming from the remineralization media. For instance, one of the materials used in the media is tourmaline, which usually contains metals including iron, magnesium, manganese, calcium, sodium, potassium, lithium, and fluorine.

We also saw an increase in toluene, from 0.04 to 0.64 PPM, which shouldn’t have come from the remineralization media. Possibly, because it was present (albeit in lower concentrations) in the unfiltered water, it may have been leaching from the plumbing.

Certain brands of PEX pipes used in plumbing have been found in a 2014 study to leach chemicals such as toluene, although it’s not clear why, in our case, toluene was higher post-purification (possibly incidental or from a component within the system itself). RO should be able to remove this contaminant, so this result is unexpected regardless of the source.

Finally, as we briefly mentioned earlier, fluoride detection in our purified water remained the same pre- and post-filtration. There are two possible reasons for this: 

• The system simply didn’t address fluoride (unusual for RO but not impossible)
• The RO did reduce fluoride, but then the remineralization media added it back in. This is possible since tourmaline (one of the remineralization media used in the system) can sometimes contain fluorine (fluoride is the ionic form of this element). We’d need to retest just the remineralization filter to confirm this hypothesis. 

Performance Certifications

Score: 6.00

Water filter manufacturers may choose to obtain performance certifications for their products, showing that they’ve been rigorously tested and verified by a trusted organization (the NSF, WQA, or IAMPO) to meet specific performance standards. 

For RO systems, NSF 58 is the most popular certification, demonstrating that the unit can consistently reduce certain impurities to safe concentrations.

The NU Aqua Efficiency Series doesn’t have any performance certifications—the manufacturer just states that it has “gone through rigorous testing”, likely in-house or from a third party rather than a certification organization. That means it received the lower score in this category. 

Sometimes, manufacturers share their own test reports online, so we can compare their data with our own testing outcomes. But we were unable to find any test data on the NU Aqua website.

🚦Filtration Rate

Score: 10.00

A big advantage of under-sink RO systems like the NU Aqua reverse osmosis unit is that, unlike countertop units, they’re powered by the water pressure in your home’s plumbing system. 

This particular NU Aqua reverse osmosis model also has an integrated booster pump to speed up the flow of water through the filters. It comes in two flow rate variations: 600 GPD (gallons per day) and 800 GPD. 

Both of these system sizes are fast enough to prevent any noticeable disruptions to water flow. Plus, because the system has its own dedicated faucet, the flow rate of water from your normal faucet (which you may use to wash dishes, for instance) will be unchanged. 

In comparison, the other under-sink RO systems we’ve tested had flow rates ranging from 80 to 1,200 GPD. 

Efficiency Ratio

Knowing the efficiency ratio of a reverse osmosis system helps us to understand how effectively the system can produce purified water and minimize wastewater production. This ratio indicates what percentage of the incoming water is actually purified, with the remaining water going to waste. 

The NU Aqua system has a 2:1 pure-to-waste ratio, making it one of the more efficient systems we’ve tested. To put that into perspective, some countertop models offer 3:1 or even 4:1 recovery rates, but conventional under-sink systems may waste up to 4 gallons of water per 1 gallon purified. 

📐 Design

Score: 8.10

The NU Aqua has a modern design for an under-sink RO system: three main filters stored inside a compact unit designed to fit easily in an under-sink cupboard, a separate post-remineralization filter and UV sterilizer, and a dedicated faucet to install at the sink.

The big selling point of a system like this is its tankless design. Manufacturers of these modern systems use technology that sends water through the filters at a fast enough rate that it can be delivered straight to the faucet with minimal delay, negating the need for a storage tank. This keeps the system streamlined and saves a ton of under-sink space. 

There’s no smart display screen on this system, but the unit itself has filter status lights that indicate when each filter needs replacing, as well as a fault indicator (detects leaks and other issues) and a power button.

NU Aqua received one of the poorer design scores we’ve awarded for an under-sink reverse osmosis system, largely because it’s the only system we’ve tested so far that doesn’t have a materials safety certification. 

Component Quality

Score: 9.50

The NU Aqua has a primarily plastic design and feels sturdy and durable. Because the filters are housed inside a solid unit, there are no flimsy components or connections on show, hopefully reducing the risk of wear and tear. 

We couldn’t find any information on the manufacturer’s website explaining the types of plastics used in the unit’s construction. We reached out to customer service, who, disappointingly, told us that they don’t have information on the specific plastics that are used to make the pipes.

Filter Design

Looking at the filters used in the NU Aqua Efficiency Series, the unit has a pretty standard setup that’s replicated across most other RO systems. The main filters include: 

• A polypropylene sediment and carbon pre-filter (removes contaminants that could damage or slip through the RO membrane)
• A granular activated coconut carbon (GAC) filter (removes additional contaminants like pesticides, herbicides, nitrates, and hydrogen sulfide)
• A reverse osmosis membrane (eliminates the majority of impurities in water)

There’s also a UV sterilization stage and an alkaline remineralization filter, both mentioned earlier in this review. 

Certification

Score: 6.00

All the other under-sink RO systems we’ve tested so far have a design certification, either for materials safety or lead-free design, which demonstrates their safety and effectiveness by meeting structural integrity standards. 

Design certifications aren’t legally required, but they reassure us that all certified parts are safe to be used as intended. NU Aqua hasn’t yet obtained any design certifications, so its score in this category was lower.

⚙️ Setup

Score: 7.00

The homeowner chose to get the NU Aqua installed by a plumber who was also installing a whole-house system for them at the same time. But the system is DIY-friendly for most folks who want to install it themselves, with only a few components and no cutting into your main water line required. 

That said, there are a couple of jobs that make setup for any under-sink RO system more difficult: 

1. Drilling into your kitchen countertop to install the dedicated faucet
2. Plumbing in the RO drainline

Given that the process isn’t as simple as for a non-RO under-sink system, the setup score we awarded was 7.00. 

If you want to see what the installation process is like before you invest in the system, you can find all the steps outlined, with pictures, in the user manual. 

Once the system is installed, you’ll just need to switch on the water connection, turn the unit on, and flush water through the filters for 10 minutes to remove any loose media. 

🔧 Maintenance

Score: 10.00

Maintenance (namely replacing the filters) is a non-negotiable task for any reverse osmosis system if you want to maintain water quality and protect the RO membrane. 

We awarded the maintenance score for the NU Aqua system based on our analysis of its servicing requirements and ongoing maintenance spend. 

Servicing Requirements

10.00

Everything about the NU Aqua is designed to make servicing as simple as possible. The filters inside the unit are twist-look, so they’re easy to remove and replace with no tools required. And with the filter indicators on the top of the unit, you can see at a glance when the filters need to be replaced. 

The homeowner hasn’t used the system for long enough to replace the filters yet, but the product listing says the filters have the following lifespans: 

• Sediment/carbon filter: 3 to 6 months
• Granular carbon filter: 6 to 12 months
• RO membrane: 24 to 36 months
• Alkaline filter: 8 to 12 months
• UV sterilizer: 6 to 7 years

We awarded the highest maintenance score to NU Aqua given the simplicity of its servicing requirements. 

Costs

Score: 10.00

To calculate the ongoing maintenance spend for the NU Aqua system, we divided its overall filter replacement cost by the filter lifespans in gallons. 

This equated to a cost-per-gallon of $0.15, based on the combined maintenance costs of each filter cartridge: 

Filter	Maintenance Cost	Capacity	Cost per Gallon
Sediment and Carbon Pre-filter	$45.95	550 gallons	$0.08
GAC filter	$45.95	1100 gallons	$0.04
RO membrane	$119.95	3200 gallons	$0.03
Remineralization Filter	$39.95	5000 gallons	$0.07

Comparably, the other under-sink RO units we’ve tested have a maintenance cost ranging from $0.11-$0.26/gallon.

🏢 Company

Score: 9.50

Beyond its product offering, we also ranked NU Aqua against other manufacturers, assessing its warranty, shipping, and returns offerings. 

Warranty

Score: 9.50

NU Aqua offers a 3-year warranty, longer than the warranties for the other under-sink systems we’ve tested so far (1-2 years).  

The warranty entitles you to a repair or replacement system at no cost if you receive a defective system. You’ll need to register for the warranty with your order number within 6 weeks of purchasing the product to be eligible. Without registering, you’re eligible for a shorter 1-year limited warranty.

The full warranty terms can be found at the end of the user manual. 

Shipping 

Score: 9.00

NU Aqua offers free shipping to all customers who spend at least $40 within the contiguous 48 states. The company also offers expedited shipping options for faster delivery. 

Free shipping is not valid in Alaska, Hawaii, and all other U.S. territories. You can see the full list on the Shipping Policy page. 

Returns

Score: 10.00

Alongside the warranty, NU Aqua also entitles customers to a 120-day money-back guarantee, which essentially means you can try the system within this time period and return it if, for whatever reason, you don’t love it. 

It gets the highest score for having one of the longest trial periods for an under-sink RO system, but there are a few stipulations to be aware of:

• You have to try the system for a full 120 days before you can return it. 
• The returns period only applies if you buy the system on the official NU Aqua website. 
• The guarantee only covers one item per household. 

You can view the NU Aqua returns policy here.

Customer Support

Finally, while customer support isn’t currently a ranking factor that influences our scoring in this category, we do just want to mention it here, since we had a lot of conversations with the NU Aqua team after our coliform bacteria test detection. 

The customer support, including how the team responded to the issues we experienced, was superb throughout the entire process. They provided replacement filters and a replacement UV light to the homeowner for free, along with a detailed sanitization guide. 

It would have been easy to place the blame on the customer and offer no help, but the fact that they provided free filter replacements shows genuine care for individual customer experience.

💰 Value For Money

Based on our testing outcomes for the NU Aqua Efficiency Series, we think it’s pretty good value for money. 

Yes, at $700+ upfront, it’s expensive. But you’re paying for the convenience of a high-efficiency, high-flow, tankless under-sink system that includes all the necessary features of an RO system, plus remineralization and UV purification. 

It’s clearly been thoughtfully designed, and (from our own experience at least), customer service is genuinely helpful and available to provide support if you’re dealing with any issues. 

The only thing that lets this system down is its lack of certifications. You can find similar systems that have been certified, both for performance and design. So if third-party proof of performance and design quality is important to you, you might want to look elsewhere. 

For instance, the Waterdrop G3 P800 is another tankless RO system that’s around $200 more expensive, but has several performance and design certifications. Read our G3 review here. 

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