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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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September 19, 2019 Mark Timmons

There are not as many differences in membranes as you think. 1:1 or 1:4 or 4:1 waste to production ratio is dictated by the water quality, not the membrane. The rest of your post is correct.

September 28, 2019 cliff

3rd paragraph, 3rd sentence: if you use 3 gallons and waste 12 gallons then there are 15 total gallons involved. 3/15 is ‘about 20% efficient’ (‘25%’ is incorrect) since you need 15 gallons (NOT 12) to get those 3.

November 01, 2019 Mark Timmons

5 out of 4 people struggle with math.

December 01, 2020 hard water stains

Yesterday, while I was at work, my cousin stole my apple ipad and tested to see
if it can survive a forty foot drop, just so she can be a youtube sensation. My apple ipad is now
destroyed and she has 83 views. I know this is completely off topic but I had
to share it with someone!

December 01, 2020 Ed

my home has 1500 parts per million coming out my well, i have a whole home RO and and iron buster system. most the time its my wife and i, but we have kids that are in and out for about half a year so its like a family of 3 really. my water coming into the house at 14 PPM now. i “lose” not “waste” 75% of my water in the process, i call it lose because the water is not destroyed, it goes right back out the house into the yard and thus back into the system where the soil filters it back in the natural system or it evaporates and comes back as rain.
RO systems are not about waste, they are about clean water and if you NEED it, you pay the cost. i cant drink our water out the well as we live near the coast in Florida and have saltwater ingress into our wells. since i put the system in my appliances are not rotting in my home, the fixtures are not caking up with scales and our glass show never needs rinsing.
maybe an RO is not for everyone but it certainly made the quality of life in our home so much better that returning 3 gallons of water to the system for each i keep is price i am willing to pay. i mean seriously what did some of you think happens to the “waste” water after your done with it? its not gone just on its way back where you got it from in the first place, be it the ground our the city’s waste water reclamation plants which means you did more harm driving for water them creating it yourself.

December 01, 2020 Ed

shoot i forgot why i was posting, i was looking for information on a dry wells size to put wastewater back in the ground without putting in on top the ground, anyone do anything like that here?

December 01, 2020 Mark Timmons

Ed, that is an environmental issue. You would have to contact your State Agency to determine if that is appropriate. However, with that level of TDS, I would prefer (personally) not to put it back into the ground.

December 13, 2020 Ed

Not sure what to do with it then, i took it out the ground and have no city sewer, right now its just evaporating or going to the storm runoff. its mostly salts, sulfur and other hard water stuff, without the salt and i am standard hardness and of course the sulfur is removed in an aerator tank . the problem is it keeps my yard wet around the ditch and i get stuck on my mower and cant get the boat across it. I know were allowed to french drain/dry well grey water out here i just dot know how big to go. is there any reason not to push it into the septic?

April 25, 2021 Mark Timmons

You can certainly try it. I know lots of people who do. It’s just a simple matter of whether your soil will accept that amount of water. It is worth a try. If that doesn’t work, I would suggest making a large French Drain. Some people take five or six 55 gallon barrels and cut the ends out, burying them and filling them with gravel. Good Luck!

April 25, 2021 Pearl Water

I read your article & I found This is really very useful and informative for those people who need to know about it. Thanks for Sharing.

September 17, 2022 Marcus

Does “RO” systems waste water? It’s a question pf perspective.
Did you “Waste” water taking a shower, or “Use” water to take a shower?
I say I “Used” some water to obtain clean drinking water by using a “RO” device; just as I “Used” water to take a shower.

I have spent many days investigating different methods of creating distilled water. Boiling water and condensing water vapor is an expensive method, yet does work well. A Solar Still is similar process using the Sun as the energy source, but requires large areas in direct sunlight all day. It is a slow process that yields about 1-1/2 gallons per day in sunny areas. Unfortunately does not work at night. “RO” systems work slowly as well, yet produce 24/7/365.

As much as I have the space and plenty of sunlight to make a solar still, the material costs and my time to build it is too much compared to buying 5 or 6 “RO” systems. Besides, a solar still will “Use” or “Waste” some water depending upon your “Perspective”!

October 23, 2022 Mark Timmons

Well stated. It is all about “Perspective.” BTW, we make whole-house RON systems, and they are very popular.

October 27, 2022 Mike

I built a water filter system.
!st level – 5 micron whole house sediment filter,
2nd level – 12gpm uv system
3rd level – 5 micron whole house charcoal filter
At this level the system splits for household purposes and to drinking water filtering system
4th level – 5 drinking water filters 4,250g capacity, VOCs, etc.
5th level – .5 micron drinking water filter
4th and 5th level for consumption, ice and cooking
This filtering system has worked for 15yrs to clean the water from my rain water collection system. Total cost for materials approximately $600
Annual filer replacement expense approximately $75.
Zero wasted water.
I originally installed an RO system not realizing the incredible amount of waste water. luckily I did run the waste to my utility room to a 5gal
bucket which allowed me to quickly see the waste water results.
I immediately removed the RO system and threw it away. As I live in New Mexico I couldn’t in good faith sell it for someone else to waste such a precious resource.
I’m guessing a good many people have RO systems are installed for them. And probably don’t realize, because most these installations run directly to a drain, how much water is actually being wasted.
My system does not treat for minerals but there are water softener systems to remove minerals. Example: EVO Whole House Water Filter and Salt-Free Softener Combo Model number: E-3000. A UV filter can also be added to this system which would eliminate the need for most if not all of the filtering system I built.
It’s a little pricey but with the current worldwide water shortage and climate change only going to make it worse I believe it is worth the expense.

November 11, 2022 Mark Timmons

You should probably read this blog that I wrote recently: Our whole house reverse osmosis systems waste a gallon of water for every 4 or 5 gallons that they make, so they are very efficient, however, you do not need Reverse Osmosis to treat Rainwater. Our systems work very well and usually require filter changes every 6 months to 1 year. Here is our most popular one: I must correct one thing that you said: The EVO Whole House Water Filter and Salt-Free Softener Combo does not remove minerals or soften the water, because it absolutely dos not remove minerals. Yes, I know they say that, but did you know that you can’t believe everything you read on the Internet? ????

February 18, 2023 Brian

Much of the most commonly available “bottled” waters are created via RO already. The issue that I haven’t seen addressed is the “water cycle”. The wastewater output of the RO system is returned to the ground, where the majority of the water percolates back into the water table. I appreciate the concerns of those on “city water” who don’t want their water bills to be increased by the amount of wastewater created by an RO system, but the amount of water on earth is a relative constant over very long periods.

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