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 refrigerator container with my Zerowater filter and my little tester from Walmart for north of $40. After just about three weeks using it for my coffee maker my wife put water in a glass for me and it tasted like saltpeter.

I tried contacting Walmart they said contact ZeroWater, it just wasn't worth the hassle. It still sits on my counter to this day.

The other issue is with their tester it lasted all of two weeks before the batteries died and there is no way to replace them. Very unhappy with an expensive transparent counter decoration.


I am so sorry I didn't research better. The reviews on Amazon gave no indication this was a problem.

Shame on ZeroWater for not addressing this issue. The water is DISGUSTING and can't be healthy for ANYONE!!!


Your biased opinion is just that. You’re not clear what you’re talking about.

Maybe check your tap water to make sure it’s not the problem. If your Zero water filter does not last, then obviously its the tap water.


So .. a.m glad i found your thread.

I thought i was wrong about the tingly lemon taste of my water all of the sudden (i live by myself so no other taste testers except my cats. As an aside, they have an aerated drinking fountain and once aerated, they will drink the water. They are extremely picky so i thought it was still ok.) I washed the pitcher, my water container in ther fridge, etc. No joy!

I then thought maybe i should not have left the filtration pitcher in the fridge??? Was some strange bacteria growing? I have used this filtration system less than a month - i live in San Diego 7 miles from the Mexican border. Few people drink tap water here!

My TDS reading was 674 without the system. It, of course, reads 0 now but the water is undrinkable straight due to the taste.

My question is - despite the taste, is the water safe to use in cooking or coffee maker? (Unfortunately i bought 2 new filters yesterday before reading this.) Maybe this is answered somewhere else and if so i apologize for being redundant.


Wow . Extremely HELPFUL .

I live in same city mentioned and it IS 700 TDS . So that explains it. So in Tennessee it IS much much lower. It also shows on the map that came with the filter .

Thank you so much for clarifying. Also great to know you have education in what you are talking about


I have a question for anyone here: If I don’t really mind the taste of the lemony water, is it okay to drink until I get new filters? Will it be harmful to me in any way? Thanks in advance!


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.


Then buy a Reverse Osmosis System. Been using Zerowater for NINE years and never had ANY problems.


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


Oh thank God i really thought some lemon juice got in one of my jugs that I filled up to keep refilling my big pitcher.


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.


You’re very confused J. Your tap water is to blame for your water tasting sour after using the filters.

400-650 TDS is massively high and bad for your health and it’s no wonder why your filter doesn’t last long and gives you a sour taste. Natural and healthy water should not have any solids in it No salt and no minerals. Your body gets minerals with the food you eat. It doesn’t need it in the water.

Would you drink ocean water with salt? Yet this person said salt is needed by the body.

Obviously this is incorrect. Your body can get sodium in veggies no problem.


I use spring water in the zero filter and I started to get the nasty taste.. so no your wrong


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

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