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

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!

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

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.

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.

Availability: In Stock
Model: CU-A4
Manufacturer: iSpring

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Motoken |

2020-03-25

After a year of drinking water daily from this filter, I can report its held up well, I'm only now returning to replace the filters as our local water in Florida is relatively pure but this makes the water taste much better. Granted we are only two people using this filter, we do almost exclusively drink water, but still its much cheaper then bottled water and tastes just as good, better sometimes. then certain brands.

susanal |

2018-01-05

We have had this filtration installed for a year now. The faucet broke after about 15 months for which I would take off a half star if I could. But the filtration system works great. The water tastes great. We go through a lot of water in my household but still have not changed out the filters. In my experience, you will notice a decline in flow or a change in taste when filters need replaced and we haven't noticed either of these. Highly recommend.

G. Weber |

2020-03-02

I thought I was saving money by buying mine here on Amazon. HOW USED WAS IT?? My water tastes even worse! The chlorine and weird taste has NOT gotten better- it's gotten more pronounced! So basically

J. M. D. |

2016-08-29

Nice product
It's simple and fairly easy to install even if, with age and my big fat hands, I'm stiffer and clumsier than ever. All the accessories&fittings are included. One quartz hole saw was needed to drill through the counter; HD has a very good one.
The customer service was impressive when I called a month or so after 1st use. A yucky black slime had appeared at the faucet! The rep was very nice and identified the probable faulty cartridge. A new one was delivered pronto and all's been fine since. First class response, no haggling!
The flow @ 55 sec/gallon feels like an eternity, lol. City water pressure is good @ 40-50 psi, so the cartridges are doing their job I guess.One strange thing: the flow has lost its smoothness. It used to run down smooth like a rope; recently, after a second, it changes to a kind of twirl (?). It looks like there's an obstruction, but removing the faucet (very easy; just lift it off the base) and cleaning/flushing is no help; the stream is still twirling, with the same pressure. No big deal, just weird.
Even though we're just the two of us and there's no way we use that much drinking/cooking water, a set of 3 new cartridges was put in 6 months after installing in Jan '16 (the fourth one is good for 1 year) as recommended by ISpring. No point defeating the purpose of the system trying to save a few bucks.
All in all, we're very happy with this system; maybe not as "pure" water as a RO, but not as much hassle either, not to mention the bulk and cost.

k schtuber |

2017-03-28

I purchased this to replace a seven year old clunky RO system that although I liked, I found the filters, connections and big heavy under counter tank difficult to navigate. Disinfecting the tank was a nightmare as well, talk about "under pressure" it's a 1/2 day to clean out the tank, change filters, re-pressurize and re-plumb everything. My only concern with swapping to this was using my mini instant hot tank. I had to replace that as well after seven years and that is what led me to getting this filtration system. I was concerned because I read a answer in regards to an instant hot question that said ;do not put hot water through filtration system" but that isn't how instant hot water mini tanks work, as they are the of the line...so I thought, I'll give it a go. The unit is quite large, you'll need about 24" x 18" linear inches on your cupboard side wall (although this unit could also stand with added support to be sure it doesn't ever fall over). All I did for install was literally swap my old in and the out lines. That's it, 2 minutes. I did run the cold for about 10 minutes to get it flowing (my feed valve is only about 1/3 open btw) and get water into the instant hot tank. I am still using my old faucet and am happy to report that the hot water tank filled right up with use of the new filtered cold water. I believe this system will be much easier to maintain and the water tastes really great, dare I say better than the RO! I also like that it is cold, the RO is room temp since it's feeding from the tank. More than enough connections and tubing is included for install should you need them. Although I am not using the faucet, it is of high quality and looks good. How fortunate are we to have the option to filter pre-treated city water that comes directly INTO our houses!!??

Tony |

2018-11-24

This filter system was very easy to install and works great. I added a line to feed the refrigerator water/ice maker and quickly realized there was a problem. The refrigerator would dispense a little bit of water and then taper off to nothing. If I turned the water filter faucet on, the refrigerator would again dispense a little bit of water and then taper to nothing again. The only way I could keep the water from the refrigerator continuously dispensing was to keep the filter faucet on. A quick call to iSpring and they told me the accompanying filter faucet was the wrong one when coupled with feeding the refrigerator. They quickly sent out a new faucet and I sent the original one back to them. The product works great and their customer service is just as good.

Deerail |

2018-06-21

Excellent filter system, good quality mount and faucet. Really like the inclusion of the membrane filter. Best tasting water we've had and have used three different systems. I like the shut off valve that eliminates turning the house water or even the under sink supply off to change filters. CAUTION, if you install it yourself, be certain to FULLY SEAT THE LINES INTO THE QUICK CONNECTS. This is mentioned in the instructions and I have used various push connectors over the years, but these required more effort to seat. The instructions mention marking the lines to be certain they are pushed in far enough. DO NOT NEGLECT TO DO THIS.

Peter |

2019-11-25

This is my second purchase of this unit, as I have moved and I left the unit behind because the buyer requested it to stay. I purchased the unit but prefer to use the European style faucet, which has a single inlet tube, because it matches better with my current kitchen faucet. This can be achieved by using the ispring apr pressure regulator installed in front of the filter unit. I've had two different ispring reverse osmosis systems which I decided to stop using because I like to have minerals in my water and the water from Ro systems tends to be a little bit more acidic and I feel like it's not hydrating me properly, but admittedly that could be all in my head, the water also just seems to taste better to me as long as you flush several gallons through it before use. I also prefer this unit to the RO systems because to change the filters is really easy, there's no tank involved, and it's far more water efficient because RO systems waste a significant amount of water just to produce filtered water. That said, if your goal is only to reduce the TDS meter reading then an RO system is the way to go because on my meter this water has the same reading as tap water, but if you want the best tasting water with a great mouth feel because of the retained minerals then this unit is by far preferable just simply due to the flavor of the water. I have contacted ispring customer support several times just because I lost a piece of equipment or needed assistance with installation, and everyone I've spoken with there has been extremely helpful, they respond within the hour, and they send me parts for free if needed and answer any questions I have. I've dealt with their representative, Nick, a few times and he especially has been extremely helpful. Nick has assisted me with the use of the different type of faucet which my wife is very happy with because it looks really nice mounted. I will say that I've never used the stock faucet so take this review with the grain of salt if you plan on using the stock faucet because I've never installed it so I don't know how its performance will be.

Joe & Anna |

2019-09-05

I am a returning customer after buying the iSpring RCC7P reverse osmosis system. If you have space I recommend the RO system. This 4 stage inline filter system is marginally better than the built in fridge water filter. My water still have a metallic taste and hint of tap water taste. I have a TDS meter and unfiltered water is 30 vs filtered water at 45. This test is done after at least 100 gallons have pass through.

BPBomber |

2020-07-08

The filter is great. The water taste great. But what I really want to address is the fact that this company stands behind their products 100%. I had the set up for about four months and a component within the faucet itself stopped working. I emailed the company, spoke to a rep named Francis, he had the company sent me a brand new faucet within three days. Then I had questions about running a waterline from the filter to my fridge for ice and water. Francis not only directed me to the parts I needed but he also sent me some of the needed parts for free. They didn’t have to do that. But they did because they are a reputable company. So if you buy from this company you can do it with peace of mind.

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CU-A4 Manual

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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.

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.

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

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