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Is Reverse Osmosis Wasteful?

by Mark Timmons May 10, 2011 70 Comments

"Don't even talk to me about reverse osmosis" said the woman on the telephone. "They waste too much water and I want to be conservative with our water resources!"

That is something I hear quite frequently and frankly, I don't understand it. Oh, I understand wanting to be conservative with our natural resources, but that same woman was driving 7 miles to town and back to get bottled water which probably was made by reverse osmosis anyway! Let's pollute the air and waste fossil fuel, but dad-gumitt, I won't waste a drop of precious water! Of course that is crazy, but let me put this in perspective. A reverse osmosis system wastes about 4 gallons of water per gallon made. If you use 3 gallons a day for drinking, cooking and internal consumption, that means you will waste about 12 gallons, making a reverse osmosis system about 25% effecient! However, US Water Systems are able to reduce water waste by up to 80%

Is that bad? Like I said, let me put it in perspective. Do you have a washing machine? Do you have a dishwasher? Why do you have a washing machine and dishwasher? Well, obviously it's to get your clothes clean and to get your dishes clean and sterilized. How efficient is your washing machine? A reverse osmosis system is 25% efficient. A washing machine and dishwasher uses electricity and hot water (which takes energy to heat) and WASTES EVERY GALLON OF WATER THEY USE.

A reverse osmosis system is not nearly that wasteful - no electricity and no wasted energy with heated water. You have a washing machine to get your clothes clean. You have a dishwasher to get your dishes clean. You think nothing of wasting water and energy to get your clothes and dishes clean, and yet you don't want a reverse osmosis system that is 25% efficient to get your water clean? Are you nuts? How long can you live without clean clothes? You might stink, but it won't kill you! How long can you live without clean dishes? You get the picture? Your body uses water to cool it and eliminate waste, but you are unwilling to waste a little water to clean your water for internal consumption? The water you drink sustains your life? You'll waste water to clean your clothes and dishes, but not to clean your water? You must be kidding!

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70 Comments

September 27, 2016 JJ

I agree that the article is belligerent. And ignorant! I don’t “waste” water washing my clothes and dishes, I use it!

September 27, 2016 Mark Timmons

So when you clean your clothes or dishes with water, you don’t waste any water, but when you clean your water with water, you waste water? WOW! You do need to go somewhere to gain perspective and maybe understand the clear and plain meaning of things. And, water that comes out of the tap is some of the cleanest and purest water in the world? I’ll have what you are smoking!

http://www.cnn.com/2016/06/28/us/epa-lead-in-u-s-water-systems/

http://www.cnn.com/2016/09/20/health/chromium-6-in-drinking-water/

There’s hundreds of more articles like this, but it’s a free country and you can choose to ignore the facts…

The fact is that Reverse Osmosis removes the largest spectrum of contaminants of any water treatment process and I think it’s worth while to waste 5 or 6 gallons a day as an investment in my family’s health. You are free to have your own opinion. Have a nice day.

September 27, 2016 Violet Mendez

I agree with you, Mr. Timmons.

March 15, 2017 Nathan

This is such an incredibly dumb analogy that I’m having trouble telling whether this article is a parody. You aren’t comparing apples to apples. This is even beyond comparing apples to oranges. It’s like comparing a car’s use of gasoline to a leaf-blower’s use, and then stating that the car has better mileage efficiency. Why not compare the car to a truck, or even a different model car?

The point is, you’re supposed to be comparing RO filtration (25% efficient) to other methods of filtration (nearly 100% efficient).

March 15, 2017 Mark Timmons

Well, thank you Nathan. I will not call you dumb, but you just have bad luck when it comes to thinking. BTW, is that that you in the picture – you look smarter than I pictured?

Actually, the point is: Reverse Osmosis removes the largest spectrum of contaminants of any water treatment process. Comparing Reverse Osmosis to filtration is like comparing a Big Mac to Kobe Beef, but you probably don’t get that either. It’s just bad luck…. I tell you.

Have a wonderful day, smart guy!

December 18, 2017 Dan

So…. what is the quality of RO waste water filtered through a gravity feed water filter? Does it make sense to purify the RO waste water?

December 19, 2017 Mark Timmons

… and then what about that waste water?

… and the waste water after that?

But, you can’t make RO water without pressure, so there really is no question here and no answer.

December 26, 2017 Chris Ringer

Mr. Timmons,
Like others, I clicked through to this article to understand how much water is wasted to produce RO water. In a water-challenged state such as California, it is my duty and desire to limit the amount of water I use and, especially, waste. Like others, I find your tone belligerent and your rationales lacking in common sense.

Regarding your comments about dishwashers and washing machines, water is not “wasted” performing these tasks, it is used. Some dishwashers and washing machines are less efficient than others and can be considered to “waste” water.

According to a brief search, the average dishwasher uses less than 6 gallons per cycle, while an Energy Star rated dishwasher can use as little as 3 gallons per cycle. So, compared to an efficient dishwasher, an inefficient dishwasher wastes as much water as making 1 gallon of RO water (6-3=3).

According to another brief search, washing machines use anywhere from 8 to 40 gallons per same-sized load. The great variation results from the variety in age and of models of washing machines. However, modern machines range between 8 and 17 gallons per load. So, compared to an efficient washing machine, an inefficient machine wastes as much water as making 3 gallons of RO water (17-8=9).

Let me put this in perspective: Rather than make 1 gallon of RO water, I could wash a load of dishes with no waste at all. Likewise, rather than make 3 gallons of RO water, I could wash a load of clothes with no waste at all.

Regarding your comments about wasting gasoline to purchase RO water in town. In your blog, you state the woman drives 14 miles round trip for the water. In this example, we don’t know whether that is the only errand the woman makes, nor do we know whether that trip results in her buying only 1 gallon of RO water. A reasonable assumption is that she combines the RO water trip with other errands. In that case, there is no wasted gas. Another reasonable assumption is that the woman buys more than 1 gallon per trip; more likely she is buying multiples of 5 gallons. Even assuming a single errand trip, the purchase of only 5 gallons, a terrible 15 mpg fuel efficiency, and a cost of $3.00 per gallon of gas, the cost to the woman for that errand is $0.60 per gallon of RO water. This can be considered “waste”. However, the moment she combines the trip with another errand, the waste cost goes to $0.00 per gallon.

Regarding the math you used in your blog. You wrote, “If you use 3 gallons a day for drinking, cooking and internal consumption, that means you will waste about 12 gallons, making a reverse osmosis system about 25% effecient (sic)!” Efficiency is based on the total amount used. In your example 3 gallons of RO water are produced and 12 gallons of waste water are produced. 3 gallons RO + 12 gallons waste = 15 gallons total. 3 gallons RO / 15 gallons total = 0.20 This means your efficiency is 20%, not 25%.

It is unclear whether you are an employee of US Water Systems. However, since you write a blog that is published on their website, the implication is that you are. As a voice of the company, what you have written, and how you have responded to comments, has resulted in the loss of a potential customer. More than that, I shall be escalating my dissatisfaction to US Water Systems’ customer service department.

December 26, 2017 Mark Timmons

I guess math is not my strong suit. Five out of four people struggle with math. While you are nitpicking and applying the word “waste” as you see fit, I happen to take it as the face value of the word. You seem to think that because your washed your dishes, it is not waste. You could use an ultrasonic device and heat to clean your dishes, so if you elect to use water, you ARE wasting it. The same is true with your clothes. You could have them dry-cleaned and thus waste no water, so contrary to your assertions, it is “waste.” Where does the water go? Down the sewer as “waste.”

I guess I value the water I put inside my body as much as I value to water I use to wash my dishes and clothes. A dishwasher wastes water, a washing machine wastes water and a Reverse Osmosis Systems wastes water, but according to you, RO recovers 20% of the water it uses. How many gallons of the water do your dishwasher and washing machine recover?

By the way: As we speak, we are developing an RO system that is 50% efficient for under-sink applications and our whole-house systems are now 80% efficient. Thanks for correcting my math!

December 26, 2017 steve papacostas

If RO (waste 4 gal to make one) system is such good at filtering water, why does it need the additional three filters, and the recuring expense, for?

February 05, 2018 Barb

Good luck with trying to educate a public that voted for the “lesser of two evils”!All things being equal, efficiency is determined by the incoming water temperature. Here in Florida, my incoming temp averages 85 degrees. My .08 – .10 cents per gallon drinking water (including the cost of my wastewater) is cheap. I use a 15k gallon chloramine filter before the RO system to maximize membrane life.
Some communities now use separate return systems to use grey water for gardening etc. Now that’s conservation!

February 19, 2018 Scott

What an interesting discussion. Thank you to all the contributors. You have highlighted so many of the issues surrounding what we mean by “waste”. I am new to RO and recently installed an “under sink” unit in our kitchen. I was surprised to see there is a connection to the “waste” pipe and to hear the dripping of the excess water down the drain. I wonder if the “waste” water could be diverted to a holding tank and used for watering the garden. Why not? That might ease the concerns of those who have a limited supply of water (and the minerals we have removed may be appreciated by the vegetables and flowers.)

February 21, 2018 Mark Timmons

It absolutely can!

February 22, 2018 Shirish

Chris Ringer’s reply is good.
Mark Timmons, your logic has flow.
I hope you realize, only 2.5 to 3% of earth’s water is “usable”.
All the water (& other base material) that we see today was created millions /billions of yrs ago when earth was created. Earth has been recycling & using it.
There was not much of the “waste” since one would need to visit well, pond, river etc to fetch/use the water.. so only required water was used.
Now that it comes to our houses directly, we need to make wise decisions.
All across the world, there is an increasing shortage of usable water.
In my language, we use word “Jeevan” which literally means life.
We can not be without water.
Consider that you waste 12 gallons a day. In a city with 100 k population the waste would be 1200K in a day. 36 MGallon in a month. imagine what would happen in a year in one city.
Hope, u will get volume of the problem.
And yes, there are places where they have to find alternative means for washing clothes, utensils, bath due to scarcity of water/ reduce frequency. If we want to avoid such scenarios (& worse) – it would be better to think & act wisely now.

What I am stating is pure facts. I have been studying on this academically & know these details.

March 03, 2018 Michael Hanson

Hmm, so the logic is, if you are already wasting water on other appliances, why not waste some more for your drinking water? Hopefully installers offer a way to catch the water for reuse outside or for cleaning. 75% waste is a lot. If you had the waste water pouring out the main faucet the same time as the reverse osmosis unit, I think many people would be disappointed.

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