iSpring CU-A4 0.01¦Ìm Ultra-Filtration Under Sink Water Filter System, Tankless 4-Stage High Capacity, Remove 99.99% Contaminants, Quick Filter Change with Brushed Nickel Faucet, White - ispringfilter Skip to content
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iSpring CU-A4 0.01μm Ultra-Filtration Under Sink Water Filter System, Tankless 4-Stage High Capacity, Remove 99.99% Contaminants, Quick Filter Change with Brushed Nickel Faucet, White

46 total reviews

Regular price $232.99
Sale price $232.99 Regular price $232.99
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iSpring CU-A4
$232.99

Features

ispring undersink filter system
contaminants that ispring CU-A4 system can remove

The CU-A4 effectively removes most problematic contaminants while maintaining a natural alkaline balance and great taste.

iSpring is America's favorite brand of water filtration systems. All of our systems go through rigorous testing for air leaks, pressure and cycle resistance to adhere to our own demanding quality and high-performance standards. You are assured of many years of trouble-free, low-maintenance peace of mind.

ispring CU-A4 provides technical customer support

We offer professional support provided by our dedicated support team based in Atlanta, GA. Our motto is: 'Just reach out – we’re here to help' – and we mean it!

ispring CU-A4 does not lower TDS value

Please note: This under sink water filtration system DOES NOT lower TDS value, instead it will keep minerals in your water. If you are interested in a filter that eliminates TDS, please consider our iSpring under sink Reverse Osmosis (RO) system RO500 or RCC7AK.

Highlighted Features

ispring CU-A4 is easy to maintain

Easy Installation And Maintenance

The CU-A4 is designed to be simple to install and simple to maintain. Push to connect fittings and color-coded tubing simplify the installation process. iSpring Twist On / Twist Off filter cartridges make changing filters a snap.

ispring CU-A4 comes with ultra filtration filter

Ultra Filtration (UF) Filter

The Ultra Filtration (UF) stage contains hollow fiber membrane technology with a pore size of just 0.01-micron, surpassing the performance of both carbon block and 'portable mini' water filters.

ispring CU-A4 comes with KDF+GAC filter

KDF + GAC

The CU-A4 is the only filter in its class to offer Kinetic Degradation Fluxion (KDF) Media which adds an important additional layer of protection to control metals.

Manuals

CU-A4 Manual Download

iSpring vs Other Brands

Feature
NSF/ANSI 58 Certification
Yes (full system certified)
Often partial or none
Verified performance & safety
Filtration Stages
Clear 3/4/5/7 stage options
Usually 4-5 stages
More complete options
Alkaline Remineralization
Available (RCC7AK/RCC7AK-UV)
Rare or expensive add-on
Better taste & pH balance
See-through 1st Stage Housing
Yes, smart flow sensor
Unavailable in most systems
Easy visual inspection
Daily Production
75 GPD (reliable output)
Often lower or overstated
Reliable daily production
Replacement Filters
Widely available & affordable
Hard or harder to find
Lower long-term cost
Installation
DIY friendly, no plumber needed
Can be more complex
Faster & easier set-up
Support & Warranty
Responsive support + solid warranty
Varies widely
Better post-purchase experience
Value for Money
High performance at competitive price
Higher price for similar specs
Better cost-effectiveness

Reviews

  • 5 stars: 43 (93%)
  • 4 stars: 2 (4%)
  • 3 stars: 1 (2%)
  • 2 stars: 0 (0%)
  • 1 star: 0 (0%)
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Anonymous
A great investment in my health!

I'm happy with my purchase: the water is definitely lighter and tastes just like water!I installed the iSpring ultrafiltration system myself and I think it's a great investment in my health. Top!Sono soddisfatto dell'acquisto: l'acqua decisamente pi leggera e sa solo di acqua.Ho installato iSpring di ultrafiltrazione da solo e penso sia un ottimo investimento per il benessere del corpo. Top!

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Anonymous
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I have been buying springs water for drinking and even that has an inconsistent taste lately. So I decided to get a water filter system and after doing some research I ended up with this one. Why? because it's compact easy to install and change filters and produce decent drinking water without waste any water.

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Anonymous
Great alternative to full RO!

I've used the 4-stage filtration system for years in multiple homes and and gifted to my family members. Great under kitchen or utility sink. Easy to install and replace filters every 6 - 12 months. This system now comes with a mechanical leak detector switch that shuts off the water to prevent flooding. Customer support is also top notch -Michele is fantastic!

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Anonymous
Great Value and Quality

Sean was really helpful and responsive to an inquiry. System came quickly. Water quality is great! My family is enjoying this product and we are looking to purchase an additional unit for the farm. Thanks ISpring!

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Anonymous
Great Customer Support

Sean has been very helpful and patient in answering my questions. They provide excellent customer service and I truly appreciate their support.

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Anonymous
The Ideal Undersink Filter

I did a ton of research on water filters many years ago after moving into a condo and looking for a way to save money on bottled water. What I wanted was something that removed the overwhelming majority of contaminants from heavy metals down to some of the more common biological ones that most filters cannot. This was the only one that could do all those things whilel also not removing important minerals from the water. It also doesn't require a huge tank under the sink that takes up space and wastes water as part of its filtration process.On top of that it's very easy to change filters comes with a water alarm to alert you of leaks and only needs its filters replaced partially every six months and fully every 12. It's very low maintenance as these things go.The customer service is also very good. They originally allowed me to substitute a different filter from the one that typically comes with the system to match my sink faucet. My one criticism is that the original filter did eventually start to leak at the base when turned on but they replaced the entire faucet for me free of charge when I reached out to their custom service for help (thanks Sean).I liked it so much that when I moved several years later I installed the exact same system into my new home. This is the filter I recommend to anyone who asks.

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Anonymous
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I like these filters a lot they do a good job and are super easy to replace. My wife has multiple chemical sensitivities and this filter works very well for her. I like to keep a spare set on hand and then when I replace simply order a set immediately for the next time.

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Anonymous
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This is the second CU-A4 system that I have put into two different fifth wheels and they are great. Most tap water taste so bad to me I can't stand to drink it but these purification systems are great and works great in a RV. I highly recommend to everyone and especially RVers.

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Anonymous
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Our faucet stopped working. Contacted support and Francis quickly diagnosed the problem and sent us a new faucet. Easy fix. System is working again. Great customer service!

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Anonymous
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I used to have an RO filter unit. This one lets the minerals in and water is tastes even better.

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Anonymous
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The taste is just as good as bought from the store. Much easier and nicer to use then the Brita pitcher we've been using for 2 years.

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Anonymous
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I am happy that I made the move and put in in. It was not difficult to install and I am not particularly handy. Water tastes good.

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Anonymous
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Very pleases with the purchase. The water definitely tastes a lot better. I installed this system by myself and I think this will be a good investment for the family.

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Anonymous
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Very happy about the purchase.

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Anonymous
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The instructions could use some more illustrations but i had no problem installing it. Very good value and i like the water.

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Anonymous
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System will have paid for itself in 6 months. It was easy to install and it doesn't make noise when it filters.

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Anonymous
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Installed next to our our kitchen sink. It was very simple to install. We use it pretty heavily to get water for drinking making coffee and cooking. I can definitely taste and smell the difference between our city water and the water coming out after passing through this water system.

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Anonymous
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They really need to work on sealing replacement filters properly. When I received them they were all broken and tips were covered with dirt. Water tastes okay ppm does not change at all from filtered vs nonfiltered; however water tastes much better than tap water

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Anonymous
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Installed on my refrigerator and it's been great. No problem at all.

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Anonymous
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Excellent product. So glad to have been able to do away with all the trips to the water fill up station.

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Anonymous
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Works like a charm. Worth every penny if you're a heavy water drinker like us. Definitely recommend.

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Anonymous
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We are happy with the product and couldn't be happier with the customer service!

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Anonymous
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This filter was very easy to install. Taste is decent not bad at all.

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Anonymous
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Easy to install. Took a while for the water to run clear. Happily ever after.

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Anonymous
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Everything is working as expect.

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Anonymous
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Our water no longer has the odor after installing this UF water filtration. Feels fresh and water flow is faster than the water dispenser in fridge.

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Anonymous
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Took us about 1/2 hour instillation time. Water still tastes good after 6 months of use.

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Anonymous
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It's pretty good but not the best.

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Anonymous
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The system fits perfectly under the sink. Very pleased with the purchase.

FAQs

What's the advantage of the under sink water filter compared to a Reverse Osmosis water system?

Great question!

1. The under sink water filter saves more space than the traditional RO water filter. Plus, it does not require a storage tank.

2. The installation process for Under Sink system is easier than RO system with tank.

3. The water filter for sink does not produce waste water. ALL Reverse Osmosis units produce waste water. With the modern technique, the waster water ratio can be reduced, but not eliminated.

4. The under sink filtration system keeps health minerals in water while removes up to 99% of most problematic pollutants such as chlorine and chlorine treatment by-products, lead, arsenic and much more.

How many gallons of water will be treated during a filter's lifespan, before they need to be replaced? Also, is there a change indicator?

The cartridge set has a capacity of 1100 gallons. However, please be aware that the actual gallon life will vary from customer to customer. As with all replaceable filter cartridges, they have limited space to hold the contaminants they remove from your water. This means that the higher concentration of junk you have in your source water, the faster the filters will run out space to keep filtering and vice versa. The filter lifespan is 6 to 9 months depending on water quality and usage.

Has anyone tested the water that comes out of the filter with a TDS meter? I checked mine today and found that the TDS was the same as the tap water.

This under sink water filtration system is not designed to remove TDS. Instead, it keeps healthy minerals in your water. If you are insterested in removing TDS, we recommend to consider a Reverse Osmosis water filter, like RCC7 & RO500.

Are Total Dissolved Solids (TDS) bad for you?

Total dissolved solids (TDS) is the term used to describe the inorganic salts and small amounts of organic matter present in solution in water. The principal constituents are usually calcium, magnesium, sodium, and potassium cations and carbonate, hydrogencarbonate, chloride, sulfate, and nitrate anions. The lower TDS means the purer water you have. However, it does NOT mean that the lower TDS the better quality the water has. Whether or not TDS are good or bad depends on what type and amount of materials in the water. Some of the minerals are healthy, while some are harmful. If you want to have a better understanding of your water quality, it is recommended to use a water test kit or get your water tested by a third-party company. For more details of how to get your water tested, you can read this article here.

Can I connect existing water line(previously connect to refrigerator,tiny size) to this under sink water filter or I have use a adaptor?

Yes. If you want to use this as a main filtered water supply, you will want to need an adapter depending on the diameter of the tubing. If you have any more questions, please contact us at (678)261-7611 or open a ticket here.

Does this remove flouride?

Unfortunately this unit does not remove fluoride. You will need reverse osmosis in order to remove fluoride.

Follow on to teeing off to icemaker: can the no-pressure faucet be used as non-air gap? if not, can a non air gap faucet be shipped instead?

This system is intended for use with a no-pressure faucet which cannot be used as a non-air gap faucet. In order to use this system with a non-air gap faucet, you would need to install a pressure regulator (APR40) leading to the system.

How many ppm does the water measure after use?

This water filtration for sink does not affect or reduce PPM or TDS.

If you want to deal with high TDS or PPM, you will want to check our Reverse Osmosis system: RCC7 & RO500.

Where can I find the replacement filter for CU-A4 and how often should I replace it?

The filter life is 6-12 months, depending on your source water quality and usage. You can find the replacement filter set here.

The order for installation is:

1st Stage: 5 Micron Sediment filter, PP.

2nd Stage: UF Hollow Fiber Membrane.

3rd Stage: KDF media.

4th Stage: Post Activated Carbon Filter.

I want to use an oil rubbed bronze faucet. Can I buy any one I want?

Yes, you can use any oil rubbed bronze faucet as long as is is an air-gap with 1/4\" connections. For more details, please contact us at (678)261-7611 or open a ticket here.

Does this under sink water filtration system filter FPAS (the forever chemical)?

We would recommend a reverse osmosis system for better removal of FPAS.

Will this under sink water filter remove pfos and pfas?

Yes, CU-A4 has a Ultra Filtration unit that can filter both.

I have a coconut sensitivity. Is there a filter I can get to replace the fourth filter on the stage 4?

Unfortunately, we do not have a replacement for them. All of our carbon filters have a coconut shell.

Does this water filter under sink remove viruses?

No, this product won't remove viruses. To remove viruses and other micro-organisms we would recommend a UV sterilizer normally found on our Reverse Osmosis systems or our whole house UV sterilizer UVF55.

I have a iSpring 7 stage R/O system that needs to be replaced due to leaks. Can I install this water filter for sink in its place?

This CU-A4 is not a Reverse Osmosis water filter. It is also smaller than your 7 stage R/O system and is designed for under sink use. We want to make sure how your old water filtration system was mounted and connected. So it is recommended to contact us directly at (678)261-7611 (M-F 9-5 ET) or open a ticket here.

Does the under sink water filter system include the brushed nickel faucet (as shown) ?

Yes. This system does include a faucet but it is the chrome colored one shown.

What size space is needed to install? Height and depth?

Product Dimensions are 10.5 x 4.5 x 12.5 inches. I'd say around 16\" x 16\" undersink space is sufficient enough to install the CUA4. It's also best if you can mount it on the cabinet wall.

Can I remove one or more of the 4 filters and still run the system?

No, all of the filters have to be in place.

Why does this under sink filter system need three tubes going into the faucet? It seems very counterintuitive!

The faucet in this under the sink water filter system not only regulates the pressure but it also works as a one-way valve that prevents backflow. The main water first goes into the faucet where high water pressure is regulated before it comes back out to feed the system.

Is ther documentation that this undersink water filter will remove all uranium from my well water?

Only Reverse Osmosis systems are proven to remove Uranium from your tap water. If you have any questions, please contact us directly at (678)261-7611 (M-F 9-5 ET) or open a ticket here.

How affective is it on arsenic?

The 0.01 micron Ultra Filtration (UF) stage removes up to 99% of most problematic pollutants including arsenic.

Can it be connected to existing faucet, what is the flow rate in GPM?

No, this intended to be used on its own separate dispenser and can't be used with the existing kitchen faucet. The flow rate is about 0.5 to 0.9 gpm.

Does the under sink water system remove all of minerals from tap water?

No, this water filter is not designed to remove all minerals from tap water. If you want to remove most minerals in your water, you will want to check our Reverse Osmosis water filtration system, such as: RCC7 & RO500.

What is the average pH of the water after filtration?

This undersink water filter has very little impact in the pH of your water.

Support

How to install
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