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Update by user Dec 20, 2016

OK, after a year and half of continuous experience on the Zero Water filter and browsing all replies following my review so far, I think I have a deeper understanding of the "problem" of this product.

I mentioned that the TDS reading of the tap water in the city I was living (McAllen, TX) was about 700 and each Zero Water cartridge did not filter more than 5 gallons of water there. Now I have moved to the Nashville area in TN, where the TDS of tap water is just a little over 100, indicating much less ions contained in the water (very good quality).

The old cartridge which already filtered 2 gallons in TX continued to give me about 15 gallons more of clean water in TN before it turned sour. Then I tried with a brand new Zero Water cartridge and it has filtered 28 gallons of water and so far it is still keeping the TDS reading at 0 after filtering. Therefore, the acidic taste at the end of the lifetime of a filter cartridge seems to reflect a capacity "problem" instead of a quality problem.

To further explain this "problem", the cations (ions carrying positive charges) and the anions (ions carrying negative charges) in water are always equal in the number of charge. Cations may include calcium ion (Ca 2+), sodium ion (Na 1+), potassium ion (K 1+), magnesium ion (Mn 2+), and so on.

Anions may include sulfate ion (SO4 2-), chloride ion (Cl 1-), carbonate ion (CO3 2-), and so on. The numbers at front of + and - signs denote the number of charge each ion carries, but this is not important if you don't care about the detail. The Zero Water filter contains an ion exchange layer, which replaces the cations with hydrogen ion (acid ion, H 1+), and replaces the anions with hydroxyl ion (basic ion, OH 1-). As you may already know (H+) and (OH-) form pure water H2O.

This is how the filter gives you pure water. Everything is fine until either ion, (H+) or (OH-), is depleted in the cartridge. In our case the hydroxyl ion (OH-) is fully consumed first, and then the anions remain in the water after filtering, and the cations are still replaced by the hydrogen ion (acid ion), finally resulting in acids, such as sulphuric acid (H2SO4), hydrochloric acid (HCl), carbonic acid (H2CO3), and so on.

That's why the water tastes sour or acidic at the end.

Finally, my suggestion is, if the TDS reading is high in your area, it may be economically preferable to just buy water from supermarkets. If the TDS values is low, Zero Water is a convenient option.

Original review posted by user May 23, 2015

I am a chemist and a polymer expert. I know what ion exchange is. I had the same sour/acidic taste experience with ZeroWater. It seems to me a design problem of this product.

Background 1: What does a filter capture?

Many other branded filters, such as Brita, DO filter some harmful organic chemicals in water using activated carbon. They don't do anything with the salts in water (not only the sodium chloride used in cooking). General salts in water are not harmful, but they don't taste good at a high concentration. ZeroWater captures cations and anions in water using the ion exchange technique, so that the salts are filtered.

Background 2: What do you know from TDS number?

The TDS meter coming with ZeroWater tests the conductivity of water. That is, it only measures the concentration of salt/ion in water instead of all solids, and estimates the amount of total dissolved solid in water. The water with a 0 reading on the meter can still contain some organic chemicals. Anyway, it's reasonable to believe the total solid left in water is very close to zero based on the so-claimed 5 stage filtering technique including an activated carbon layer. However, a totally pure water is not good to health in fact. If you read a TDS value of 30 from a bottled spring water, it doesn't mean the water is not good. Instead, the water contains some minerals/salts needed by your body. Sometimes I added a small fraction of Brita filtered water in the ZeroWater to tune it to below 50 TDS.

Problem of ZeroWater:

After flushing the ZeroWater filter I started to enjoy the filtered water, which was much cleaner than the tap water (TDS around 700). However, after about 5 gallons of water were filtered, the filtered water turned bad and tasted extremely sour/acidic as many people had experienced. I noticed at that time that the flow rate of the filter was faster than before and some gas bubbles came out from the orifice at the bottom of the filter. The sour taste indicated there might be still a large amount of hydrogen ions available in the filter, and the filter should still have a considerable lifetime. It seemed that some structure in the filter was crushed because of the build-up of filtered substance or increased pressure inside, so the chemical holding hydrogen ions leaked out. The flow rate might be much faster due to the damage, taking out the small amount of air that would be otherwise locked inside the filter.

Hope this comment is useful to both the users and the engineering department of ZeroWater.

Product or Service Mentioned: Zerowater Filter.

Reason of review: Bad quality.

Monetary Loss: $40.

Preferred solution: Let the company propose a solution.

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Same issue here after about 15 gallons of tap water (TDS 128). If I have to buy filters at this rate, I will go back to my Brita fds

I have looked this up because our filter is only working for 2 weeks, I am about 625 reading to start. I am buying water until we get back to Colorado.

Then I will try it again. The filters are way to expensive to keep buying and replacing every 2 weeks.

The worst part is my old put pitcher did not make my water taste bad after 2 weeks it filtered for at least 2 months before changing. I am not happy.


So very disappointing After only just over a week Water is as sour as if I had added lemon What a waste


I will never buy this product again!!!!!!!!!! Filter is a waste of money!!!!!!


Agree with last few posts. Water tested here >300. After ZeroWater filter


*** this product. I replaced the filter not even a week ago and it already tastes like the water equivalent of sour milk. I'm glad I'm using it as the guest in someone's house and that I didn't make the mistake of buying it myself.


thanks for explaining why zero water gets this sour taste. The city I live in has pretty good water and the meter read it in the 400s to 650 out of the tap.

However, for the cost of the filters they do not last long enough for me. I'm going back to Brita that does not taste like something toxic when the filter starts to dump leftover chemicals into the water.

Yuck. Thanks again for the article.


I am trying to understand what to expect from this filter, although it is working fine at the moment, TDS reads 000. I can see how the taste can change at the end of life of the filter, as cations and anions are filtered by different granules.

Interesting that the anion DI resin becomes saturated before the cation resin -- this might be related to water fluoridation... Would it be possible to add more of the anion DI resin in the mix, or you are using a premixed fill, like Tulsion MB-115?All together, it's an excellent filter for the office, while nothing beats RO for higher usage at home.


Purchased the 35 cup zero water filter a couple weeks ago from Amazon. Our municipal water TDS or ec is around 200.

and ph is around 6.8.I use the water for indoor gardening so i ph it coming out of the filter and found it to be at 3.0 or less! It is incredibly hard to adjust with various pH adjusting solutions, which really sucks because the low TDS is nice. I'm not by any means a chemist , but the ion explanation at the top of this thread helped a lot. I'm very disappointed in this product and will never purchased one again.

Today I read 2.5 on my pH meter which has been calibrated very recently. I was sitting there thinking I can't believe people drink this!!!


Total waste of money. 3 days and my water is not drinkable with this HOS.

Been using Brita for 13 years and fell trap to their pretty ads on TV.

They should be more honest , very misleading. The Brita is back in the fridge and our water tasting great again

to Brian F #1424380

Do not buy this product! Shame on this product

to Brian F #1496974

Me too!


I just bought this system and in less than a week we've used two filters and the sour taste is ridiculous but my little TDS Tester says that we have anywhere fr 0 - 2 in our water. We live in Vegas where pretty much everything is sh!tty and our water is no exception, it has a whopping 500+... I had this system a few years back while living in California and never experienced a sour taste

Troy, Missouri, United States #1344717

I'm in an area notorious for bad water. I decided to try the zero water filtration system (due to the large amount of advertising-I purchased it over the Brita).

On the second day I'm googling "Funny taste with Zero Water". I found many postings indicating it's not going to work for me. Actually I didn't need the confirmation that there's something very different about these filters.

Rather than asking family or friends the silly "Taste thus-does it taste bad" (here-confirm this is gross)...Just go with the botulism rule "When it doubt, throw it out". Or return it-they're ridiculously expensive.


Hello, I live in Florida. My water tastes fairly neutral out of the tap, 180 TDS, maybe just a little over chlorinated.

I experience the sour taste from zero water filter after about 5 gallons of filtration. Your explanation regarding the chemistry makes sense. Per the chemistry, the basic ions have been depleted and there is an abundance of charged ions, causing the sour taste, right?

So then filtering more water through the system should eventually deplete all acid ions as well? At some point, you should end up with the same neutral taste you began with?

Tempe, Arizona, United States #1264156

We have exactly the same problem. Just 4 days, the water is not drinkable.

We are in Arizona.

Not sure what is Walmart's refund policy for this ***. I will bring it to Walmart for a refund tomorrow.

Lafayette, Colorado, United States #1261164

Hello! Thank you for this explanation.

The water were I am at is decent at 154 TDS says the zero water site. I haven't purchased this system yet nor tested my specific water out of the tap.

My question lies within a double filter method proposed by a reviewer on amazon. He suggests to use a first stage zero water filter past it's normal lifespan of 006.

Then you will have a second stage filter that gets a fairly low TDS water. This way the second stage filter will last a long time. Then once the secondary filter gets to 006, you move that one into the first stage position and put a new filter as the second stage.

I am wondering, based on your review of how the ion exchange can become unbalanced, if you think the dual stage filtering is a bad idea.

Do you think that the water from the primary will cause an opposite imbalance in the ions of the secondary filter and make the water harmful in some way? If so, do you think this would only be an issue with water of a very high starting TDS or even doing the dual stage for lower TDS will still cause this imbalance?

to Kirk Mcallen, Texas, United States #1261473

Hi Kirk! The two-stage filtration is a natual solution that people would figure out to last the lifetime of the filter cartridges.

This will be very helpful if the first depletion of an ion source is random between hydrogen ion (acid ion) and hydroxyl ion (basic ion). However, it seems so far that the basic ions are always depleted sooner than the acid ions, based on all reviews I have read. In this case the two-stage filtration system can save a large number of acid ions in the cartridge at the second stage. The number of basic ions saved by using the two-stage filtration system depends on how quickly the TDS turns bad from 1 to near the value of tap water, i.e.

how many basic ions are left for the final extraction. Generally, this is not a long process when the ion exchange layer gets to the end of the lifetime. Other than the ion exchange layer, the active carbon layer may be also saturated by contaminants for an extended filtration if the contamination in the water is high. The clogging will slow down the stream.

As a conclusion, the two-stage filtration system helps to a small extent to extend the lifetime of the cartridge, and I don't expect harmful materials if the final TDS is 0.

This is based on the assumption that the sour taste comes from the early depletion of basic ions.

By the way, I generally change the filter cartridge once I notice the sour taste (TDS is 1 or 2). I don't like that taste and I don't think drinking sour water is good for health, unless it's vinegar drink.

to kerinlau #1390835

Here in Newport News VA we have a TDS reading of 130ppm.

We tried the double filter method with an old filter but found the old filter TDS reading quickly exceeded our starting 130 ppm and went way higher and shortened the life of the new filter.

We abandoned the double filter method.

Thank you for explaining the details of how the filter works.

Phoenix, Arizona, United States #1250319

Nothing has changed, its Dec. 2016 and the filter has only cleaned about 3 gallons of water before the turning distasteful.

If I had known the filter was so short lived I would not have purchased this Zero Water jug. I purchased from Walmart in San Diego for $31.88 + tax. I got approx 3 gallons of fresh tasting water. I could have purchased 30 gallons of clean water for that price; or .50 cents for 5 gallons in Yuma AZ.

I wish I had read reviews before purchasing.

And the only thing I can suggest to the co. for good customer service is offer filters at a very low price since we who own these need to be thanked not gouged. I suggest they offer 1st.

time orders a very good deal or there will be no ordering of replacement from this customer.

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