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Why is the TDS on my RO system so high?

by Mark Timmons November 20, 2013 49 Comments

Dear Sir,

With your 40 years experience in drinking water, I'm hoping you can help. At this point I'm worried and confused about the new drinking water system we just had installed in our home by a local company that we will be renting from.

For the past 17 years we have been renting a Reverse Osmosis system (4 Stage) from a company that does supply or install ro/alkaline filter equipment. Our equipment is under the kitchen sink. I thought RO water was healthier for myself and my family. I recently read that RO water is Acidic water because it takes all the minerals out. I was told by a friend that adding an Alkaline filter to our RO system would make the water more alkaline which is healthier for the body. This past Wednesday, I had a 6-Stage Reverse Osmosis/Alkaline Ionized Water filter system installed by a different company. I read it would be healthier because the alkaline filter adds Minerals back into the water which makes the water more Alkaline. Drinking a more alkaline water supposedly makes the body less acidic.

The RO water I had before always tested between 10-20 (company serviced every year or sooner if needed). I have a HM digital TDS meter tester and would check it myself now and then.

The new company is family operated. The wife did a lot of research before adding this alkaline ionized filter to their RO systems. She claims it's one of the best filters out there. Her older son takes care of the water system for the military so I thought this was a great testimonial.

Before they installed our new system, we tested my water from my "old" RO water system, it tested 12, both on my tester and his. After our new RO/Alkaline Ionized filter water system was installed it tested at 49. He said it's higher because of the minerals added back into the water. He also told me to drain the tank tonight and in the morning re-test the water, it should be much lower probably in the 20's. In the morning it was 72. This made me worried about drinking this water. I called the owner and she was surprised that it was that high & said she would call the manufacturer and get back to me. I tested the water again this morning, and it's even Higher, 96. As I said at the beginning of this long email, I'm worried about this water and don't know if we should be even drinking it.

When I saw your site and with all your experience in this field I thought you could tell me what's happening & if we should be drinking this water. We also buy bottled water to take out with us. We buy "DaSani" water. I tested the DaSani, it was 24. DaSani claims they add a very small amount of minerals back into their RO water for taste. I thought 24 is a pretty good # for bottled water. Which makes me more confused as to why my new system is testing out so high.

I hope you can help. I would be more happy to pay you a fee for your unbiased opinion on this water situation, please let me know. It would be worth it for someone with your experience.

Regards,

I.S. - Westlake Village, California

The Water Doctor responded:

First of all, the debate about Alkaline verses Acidic water is sad, because most people do not understand the difference, and there are lots of unscrupulous companies competing for the business. For the record, I do not think a few points on the pH scale make a difference because you drink the water and the water penetrates the cell wall, it becomes the pH of the body anyway.

You have evidently purchased a reverse osmosis system that adds minerals back to the water (usually calcium carbonate) which is why your TDS is higher than before. Your RO is taking the minerals out and the re-mineralization filter is adding some back. It is functioning perfectly in all likelihood. No matter what the label says, you do not have a Alkaline Ionized filter. You have a RO system where additional minerals are added which adds TDS (Total Dissolved Solids) back to the water.

Some manufacturers say that they have ionized alkaline water, but unless the ORP (Oxidation Reduction Potential) is lowered and the pH (potential of Hydrogen) is raised and alkalinity added, you cannot change the alkalinity. The water may be alkaline in nature (pH above 7.0) but it does not add alkalinity and there is no benefit to that.

The people you bought the RO from are probably innocent of any deception, simply uneducated about these things, but just adding minerals to raise the pH (and TDS) really does nothing. To have alkaline water, you would have to use an alkaline water ionizer (an electrical device that uses electrolysis), but that may not be wise either, simply because you can't use RO water to make alkaline water. You have to leave the contaminants, and then you concentrate all the impurities removed by reverse osmosis. A good ionizer can cost up to $7,000.00! Silly, in my opinion when you can simply do one of two things:

mineral-water-sparkling
  1. Use 1/2 teaspoon of baking soda in 12 ounces of water once a day; or
  2. Use Gerolsteiner Mineral Water once a day.
*I am not a medical doctor (well I am a water doctor) and this is not medical advice, but Alkaline Ionizers are not the solution. The two above methods can produce true alkaline water, but you are not getting it from your reverse osmosis system. You may want to read, a previous blog post I have written on Alkaline vs. Acid Water.

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49 Comments

June 23, 2017 Mark Timmons

What kind of RO do you have ?

How old is is?

What is your incoming TDS?

I need a lot more info in order to answer your question.

July 13, 2017 Cecilia Ghilardotti

Hi, I just got an RO system that adds back minerals as well and the TDS meter reads 96 from it. The tap water reads 372. Is this a normal level to have for an RO system? The RO is from Aquasana, I just installed it so it is pretty much new.

Additional info: the guy that installed it, who apparently has 25 years installing RO’s, said he thought there was something wrong because the water from the RO faucet came full force as soon as the RO was installed. He said that water first drips until tank fills up, he thought the membrane was not working. He measured TDS then and both tap and RO were 230. When called Aquasana, the tech said that since the installation guy hooked the refrigerator’s icemaker to the RO that probably caused the water from the icemaker to flow back and come out of the faucet.. In any case, they recommended purging the system for 24 hs and then try again. After doing that, the water intensity from the faucet lowered to the normal level when the tank emptied. But now testing the TDS, 96 seems too high to me for an RO system?

July 14, 2017 Mark Timmons

Yes, it is too high. You might as well not have an RO. Really, adding back minerals is useless (unless it is for taste) because even if you drank a bathtub full of highly mineralized water a day, you would not get 5% of the minerals your body needs. Water is not a significant source of minerals.

July 14, 2017 Itay

I read somewhere that RO water which has low TDS (total dissolved solids) is not good to drink long term due to the fact the water has a demand. Is it true that if the water lacks minerals, it will begin to feed off the calcium in your bones deeming them brittle over time?
Hence, RO purifies the water and then being reintroduced with minerals to feed the “demand” in the water therefore not feeding off of us while also making them less acidic?
I have been also reading about PFAS and PFOS and trying to figure out the best way to cleanse my family’s drinking water in the right way.

Your feedback is greatly appreciated.

October 09, 2017 Tyler

I have a spectrapure ro/so my ppm read 10-16. I noticed it’s radon n 240-250 my water is well water and it reads 260’s. I replaced the carbon and micron filter but I ran out of di resin for now. My ppm has not went back down it’s still 240-250. Could this be because of the resin is old?

October 16, 2017 Mark Timmons

Most likely, but we need more info… specifically a Lab Water Test.

October 31, 2017 John Carlson

My water before the r/o system is a little over 600ppm. After the filter it’s 60 so about 1/10 of the initial water. I have read this is normal to reduce by 90% but need a professionals opinion. Thanks in advance

November 05, 2017 Mark Timmons

That is acceptable!

March 16, 2018 shah

No need to remineralize. WE got mineral from our food.

March 18, 2018 Mark Timmons

Exactly! That is correct.

April 17, 2018 Deb

Hi – We have well water and have an RO system installed under our sink. I just bought a Zerowater water pitcher and it has a TDS tester with it. I tested our water from the tap and it was 133 and then tested from the RO tap and it was 633. I took another sample and that one was 690. Then I tested the water after it went through the Zerowater filter and it was 0. We also get bottled water and it tested at 002. I don’t understand how the RO water can be that high. Thank you.

April 28, 2018 Mark Timmons

Zerowater uses DI resin, so of course, it will be ZERO, but on your water, it might only last a few gallons. What is the TDS of your water before it is treated?

April 28, 2018 Hank

I have a great question….i test my uri e its 5.5 rough avg…i drink high alkiline water, it goes up. Why? If i add banking soda it goes up into the 7’s…why is this? if your stomach acid neutralizes alkilinty in water then my ph shouldnt change, right?

August 08, 2020 Mark Timmons

No, that is not true. #1: I believe that RO removes the widest spectrum of contaminants and why on earth would anyone not want to remove as many contaminants as possible; #2: There are things that can be done after the RO process to enhance the water quality. We are currently developing a new Process and Products, called Livation Hydration Technology which requires a different way of looking at and treating water. We hope to release it very soon.

August 15, 2020 Mark Timmons

Once the water penetrates the cell wall, it becomes the pH of your body, so that is not true. We are coming out with a new 100% American-Made RO that is also available with Livation Hydration Technology… a new technology that includes true alkaline water, higher pH, lower ORP and molecular hydrogen, Watch for it. PFAS and PFOA are best removed with carbon filtration and reverse osmosis for drinking. We are seeing more and more people opt for whole-house RO Systems. This is what we use on PFAS: https://www.uswatersystems.com/pioneer-lead-cyst-pfoa-pfos-removal-system.html

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