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.

Location: Mcallen, Texas

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I purchased my first zero water filter about 5 years ago and it was the standard size. I used it on a regular basis for what seemed like over a year.

I may have filtered at least 50 gallons worth of water over that ntime period before I started to notice the acidic lemony metal spoon-like flavor. I eventually replaced it with the Mack daddy big boy zero water pitcher that holds way more. Within a couple months of getting the upgraded model, I started to get the tingly taste. I have moved to a different town which has a different water supplier but the levels out of the tap are about the same.

I'm just wondering how I got so much more use from my previous pitcher before having to change the filter. I also have a cheap *** $15 Brita filter mounted to my sink, but that didn't do a *** thing to the water except make it flow from the sink nice and smooth. The water literally had the same reading on the water tester whether it came out of the Brita or just straight from the faucet!

Whats up with that? I just can't win with either of these *** filters lol


If the water quality in your area was superb, say the TDS reading was below 80, it's possible for a single filter to process 50 gallons of tap water. Of course the TDS number only reflects one aspect of the water quality, the electrically conductive component in water.

Brita does not filter this component but does some other, such as some organic components. That's why the TDS reading did not change after the water was filtered by Brita. How soon the ZeroWater filter turns acidic mostly depends on how high the TDS reading is.

The filter can be interpreted as a "clean ion" supplier. High TDS water consumes the "clean ion" quicker.



We experienced the same acidic taste after filtering 2 days of water. So this happened quite quickly. Is there a way to fix this?




Maybe this is the situation in your area. Please try to count the number of gallons each your filter works on before it goes bad.

In my area the TDS of tap water is 600-700 and each filter works well on 5 gallons. If your tap water has a TDS of 300, for examples, your filter may be able to give you about 9-10 gallons of pure water. Considering it's purer than the bottled pure water, this performance may not be bad. Since people always open the box with high expectation and don't count the gallons for the first filter, they are generally disappointed at the beginning.

I suggest you follow a couple of replacement filters. The performance of their filters is pretty stable to me.


I have the same experience for the last 4 months since I use Zero water. The filters go really fast annd the water starts taste badly -acidic... It should not be the case with such pricey products.


I think they keep it like that so you have to buy a lot more expensive filters. I went back to Brita. I've had my tap water before, Brita is better than unfiltered and doesn't soil itself to empty your wallet.


Beckster, Yes, the filters are expensive. That's understandable, since from my professional point of view this filtering requirement costs more money to make the filters indeed.

Their filtered water is better than that filtered by Brita undoubtedly. My suggestion about the price would be to buy replacement filters from a retailer where you can use a coupon.


My wife and I recently purchased the ZeroWater 23 Cup Dispenser from Walmart and thought it was an upgrade from a similar size Brita water filter. Today we smelled a sour or fishy smell coming from the ZeroWater dispenser and found mold on the filter.

It makes since now because we have been complaining about mild headaches, stomach bloating, and restless sleep. Now we have to pay for a doctors visit.



Thank you for your responses Kerinlau!


We've only had a zerowater pitcher three days and it's hardly filtering any water at all. :-(


Kerinlau...so after reading your hypothesis on this brand of filtered water systems, I am now more confused than ever. I understand everything you stated in your points.

I just don't know which way to turn now. I currently own a "Bobble" water bottle, and previously a Brita water bottle, and after reading many reviews and such, I don't feel as if it's safe or conducive to be drinking out of this bottle anymore. I just need something that can filter the bad tastes and the bad toxins/bacteria out of my water. Water is all i drink, but I'm always on the move....home, waitressing, at the gym, hiking, traveling.

I need something that will virtually work for every water source. Any suggestions?



Brandi, Sorry for the confusion from my post, in which I only shared my engineering thought without intention of giving any suggestion. As for your need about portable drinking water, I would suggest general filtering bottles with activated carbon fiters, such as Brita and Bobble, if your local tap water is not very salty.

That way most organic and inorganic chemicals are filtered. If your local tap water contains a high concentration of salt (TDS >300), the current best choice would still be ZeroWater, with bottled spring water for the mineral needs of your body. I would not be worried by bacteria as that is controlled by the chlorine in the tap water, but whenever the filtered water tastes funny or strange, it could be due to the toxin caused by algae, especially in summer. Boiling the water to let it evaporate before drinking would be my suggestion in this case.

BTW, Brita filters many chemicals as ZeroWater does, just not by a percentage as high as ZeroWater does. Hope this helps a little.


Kerinlau...We recently bought a ZeroWater and have begun to notice a lemony taste. I am still not understanding your recommendation?...If the ZeroWater tastes like it has a lemon in it, is this harmful and do we need to get rid of it?

It seems from reading other's experience, this is a "defect" of ZeroWater.

It seems as though something needs to be done by ZeroWater. We formally used a Brita and had no problems with the taste of the water.


I have consumed three ZeroWater filters, and none of them filtered more than 5 gallons before the lemony taste came out. Not sure if it's due to defect, but it's the current life time of the filters for my tap water. Don't drink the water when it gets lemony.


So, is the lemon taste harmful? We have a ZeroWater with a lemon taste. Does not seem normal and is this harmful?


The lemon taste is from the chemical inside the filter. Some users said it brought up flu like symptom. I suggest change the filter when it starts to taste sour.


kerinlau, that is what Zerowater wants. Those filters are expensive.

They have short periods of use. It's like printer ink but with a necessary element of life.

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